Biomass Valorisation Resources, Opportunities, and Barriers in Ireland: A Case Study of Counties Monaghan and Tipperary

Abstract

Agriculture is Ireland’s largest sector with agri-food exports amounting to EUR 15.2B in 2021. However, agriculture is also Ireland’s largest contributor to GHGs, accounting for 37.4% of emissions in 2020. Developing indigenous renewable energy sources is a national objective towards reducing GHG emissions. The National Policy Statement on the Bioeconomy of Ireland advises a cascading principle of biomass use, where higher-value applications are derived from biomass before energy generation. This research quantifies and characterises biomass wastes at farms, food production, and forestry settings in counties Monaghan and Tipperary, Ireland. Value chains, along with Sankey diagrams, are presented, which identify biomass that can be exploited for valorisation and show their fates in industry/environment. The quantity of biomass wastes available for valorisation under Business as Usual (BAU) vs. Best-Case Scenario (BCS) models is presented. BCS assumes a co-operative system to increase the feedstock available for valorisation. In Monaghan, 73 t of biomass waste vs. 240 t are available for valorisation under Scenario A vs. Scenario B, respectively. In contrast, in Tipperary, a 7-fold increase in biomass waste is achieved, comparing Scenario A (126 t) against Scenario B (905 t). This highlights the importance of engaging local stakeholders to build co-operative models for biomass valorisation. Not only is this environmentally beneficial, but also socially and economically advantageous. Creating indigenous fertiliser and energy sources is important for the island of Ireland, not only in meeting market demand, but also in reducing greenhouse gas (GHG) emissions and achieving emission reduction targets.

1. Introduction

Global food output has increased threefold since the mid-1900s, expanding faster than both population and the area of cultivated land. This escalation has been powered by technological innovations aimed chiefly at maximising yields and economic returns [1]. Climate change commitments and the shift toward a circular bioeconomy are driving countries worldwide to replace fossil-based value chains with renewable, resource-efficient ones [2]. Within Europe, the Green Deal and the updated European Union (EU) Bioeconomy Strategy place particular emphasis on turning agricultural, food-processing, and forestry residues into higher-value products before energy recovery [3]. Valorisation is the process of converting research and innovation outputs to create value. This is often performed by linking different sectors and making knowledge available for societal benefit. EU Green Deal measures, including the “Fit for 55” package, depend on this process to convert scientific advances into practical tools that support a circular, sustainable economy.

Ireland’s agri-food system comprises 140,000 individual farms in Ireland, with 66% of the land footprint dedicated to agricultural use [4]. According to Bord Bia [5], the Irish beef market will grow due to increased demand for beef with high-quality assurance and sustainability standards. Poultry is the fastest-growing sector in this area, and pork is the most widely consumed meat in the world [6]. With this intensification of meat production comes a challenge in managing animal by-products, manure, and GHG emissions. This makes it essential for Ireland to maintain its status as a leader in crop production, with the highest average wheat yields and the second-highest barley yields [5,7]. Barley and wheat straw are primarily used for animal feed, and this demand is likely to increase due to growth in the dairy and livestock sectors [7]. Oats are a traditional Irish crop grown to feed horses, but now mainly to feed people and sport horses; demand for oats will increase by at least 50% over the next eight years [7]. However, expanded crop growth leads to increased GHG emissions from fertiliser production and the breakdown of fertiliser on soils [8].

Forestry cover in Ireland is estimated to be at its highest level in 350 years, with 11% coverage, and is expected to more than double by 2035 [6]. Substantial volumes of residual biomass, including the branches and tops left at harvest sites and the sawdust, offcuts and shavings produced in sawmills accumulate across the forestry sector [7,8]. When appropriate conversion technologies are employed, these by-products can be redirected from waste streams into renewable energy generation. Realising this shift sustainably will hinge on a system-wide transformation that combines farm-level data collection with the development of new, integrated value chains, thereby underpinning the long-term viability of Ireland’s increasingly intensified agricultural and forestry industries [9,10].

Developing indigenous renewable energy sources is a key national objective towards reducing GHG emissions. However, there are competing demands on biomass for food, feed, fuel, and functional material. The National Policy Statement on the Bioeconomy of Ireland advises a cascading principle of biomass use, where higher-value applications are derived from biomass before being used for energy generation. Agricultural and forestry wastes have the highest potential for biorefining, but access to these materials is an obstacle [11].

This paper quantifies biomass wastes at farms, food production, and forestry settings in counties Monaghan and Tipperary, Ireland. The characteristics of the biomass wastes are discussed in relation to their potential technology valorisation pathways. “Valorisation” is defined as any process that upgrades these wastes into materials, chemicals, fuels, or energy. Current conventional value chains are presented that identify biomass wastes that can be exploited for valorisation, along with Sankey diagrams showing the current fates of these wastes. Using this information and estimates from industry, the amount of biomass wastes available for valorisation using a Business as Usual (BAU) vs. Best-Case Scenario (BCS) model are presented that assumes maximal technical and logistical recovery. Alongside this, stakeholder views on opportunities and barriers associated with biomass wastes valorisation are presented. This research presents important insights on the quantification and sustainability of biomass for the developing bioeconomy, emphasising the importance of stakeholder engagement in the development of sustainable value chains for the bioeconomy.

2. Material and Methods

2.1. Biomass Resources Available from Waste Streams

The approach taken for this study is a resource-focused rather than demand-driven approach [12]. A resource approach focuses on the resource base and the competition between different uses of the resources. In contrast, a demand-driven approach focuses on the estimated amount of biomass required to meet energy demand. This research aims to create a cascading system of biomass use; therefore, a resource-focused approach is used. This approach enables quantification of biomass resources to feed emerging bioeconomy processes. The range of biomass resources available from each source in Monaghan and Tipperary is outlined in

Table 1. Range of biomass resources available from wastes.

Main Type	Sub-Type	Examples
Livestock/ Poultry	Manure	Pig manure, chicken manure, cow manure
Crops/Horticulture	Primary or harvesting residues, by-products of cultivation and harvesting activities	Wheat straw, barley straw, oat straw
	Secondary processing residues of agricultural products, e.g., for food or feed production	Spent mushroom compost, mushroom offcuts
Forestry	Primary forest products	Stemwood, thinnings
	Primary forestry residues	Leftovers from harvesting: twigs, branches, stumps
	Secondary forestry residues	Residues resulting from processing: sawdust, bark, black liquor

.

The most up-to-date quantities of livestock, poultry, and crops at the time of publishing were gathered from the Irish Central Statistics Office (CSO) [13] website. Data from 2020 was available for cattle, 2018 data was gathered for pigs and sheep, while the most recent data for poultry dated from 2010. The biomass database Phyllis2 was used to gather data on physicochemical composition of (treated) lignocellulosic biomass, micro- and macroalgae, various feedstocks for biogas production, and biochar [14]. Table S1 reports class-specific manure mass factors (t animal⁻¹ yr⁻¹, as-excreted) aligned to CSO categories (e.g., dairy cow, dry cow, bulls, heifers, calves, pigs, poultry), compiled from the ASABE/ASAE D384.2 Manure Production and Characteristics standard [15], with the class stratification implemented following the Ohio Livestock Manure Management Guide [16]. This permits like-for-like pairing with local headcounts for each animal class.

2.2. Calculation of Available Biomass

“Available for valorisation” refers solely to biomass that can be diverted from its current low-value uses, such as land application of logging residues or on-site energy combustion, after existing high-value outlets, such as board mills, animal bedding, and stakes are retained. Livestock and poultry populations for Monaghan and Tipperary are shown in Table 2. The flows coloured orange (land application and on-site energy) are classed as recoverable; their masses generate the “available for valorisation” totals reported in Table 3. Crops and associated waste outputs are detailed in Table 4 and the quantities of crop residues available for valorisation are presented in Table 5. Forestry biomass available for valorisation is summarised in Table 6, while stakeholder clusters are outlined in Table 7. Finally, the recovery factors applied across all biomass categories are presented in Table 8. The main biomasses focused on in Monaghan and Tipperary, as in many regional locations across the globe, are farming, food production, and forestry residues. The rationale for concentrating on these resources to feed the bioeconomy is as follows:

• These materials are generally considered a nuisance and raise a challenge for disposal without polluting the environment.
• New biorefinery processes must be based on non-competing wastes and residues to reduce impacts on food availability and prices.
• Bio-based economy is fundamentally based on using biological processes to create energy rather than fossil fuels.

2.3. Stakeholder Perspective

Stakeholder workshops were held to gather farmers’, foresters’, and food producers’ opinions on valorising biomass wastes, considering four themes: Market, Feedstocks, Logistics, and Knowledge/Communication. Linking with key stakeholders (primary producers, industry associations, etc.) ensures that new bioeconomy value chains are developed in a realistic manner, accounting for constraints identified by stakeholders.

3. Results

3.1. Livestock and Poultry

Table 2 displays the livestock and poultry head counts for counties Monaghan and Tipperary. Holding over half of Ireland’s poultry, Monaghan is a major poultry producer, while Tipperary primarily focuses on cattle production, specifically dairy cows. Livestock and poultry produce vastly different amounts of manure, with dairy cows producing the largest amount of manure due to a higher intake of food compared to other animals (see Table S1 for manure production by animal). Dairy cows produce the largest amount of manure per kg of animal weight (0.036 t/kg animal/year), followed by broiler-table birds (0.033 t/kg animal/year) and heifers (0.032 t/kg animal/year) (Figure S1 displays data for all animal categories). Value chains (Supplementary Materials Figures S2–S4) have been produced to depict the current conventional system with regard to poultry, pig/sheep, and cattle farming and processing in Ireland. These value chains are used to identify where wastes are already utilised and where opportunities exist to use waste as a resource. Considering existing systems and products that would be affected by the uptake of new bioeconomy valorisation pathways is essential to quantify environmental benefits and trade-offs from avoided products. From interviews with stakeholders, it was stated that there is little “waste” arising from the production of meat, with most category 3 wastes (raw meat, hides, offal, etc.) being transported for further processing into pharmaceutical products, animal feed, etc., as shown in the value chain diagrams. The most common waste issue raised by stakeholders was manure.

Table 2. Animal head numbers and manure production in Monaghan and Tipperary.

Animal Category	Monaghan Heads	Tipperary Heads	Monaghan/Tipperary Share (%) †
Dairy cows	38,100	182,500	17.3/82.7
Dry cows	31,100	53,600	36.7/63.3
Bulls	1700	3800	30.9/69.1
Cattle male ≥ 2 yr	11,200	47,600	19.0/81.0
Heifer ≥ 2 yr	14,300	29,500	32.6/67.4
Cattle male 1–2 yr	27,100	87,400	23.7/76.3
Heifer 1–2 yr	31,300	96,900	24.4/75.6
Male calf < 1 yr	30,300	102,100	22.9/77.1
Female calf < 1 yr	31,800	103,600	23.5/76.5
Cattle total	216,900	707,000	23.5/76.5
Laying birds	910,936	7809	99.2/0.8
Breeding birds	197,418	305	99.8/0.2
Broiler (table) birds	4,459,667	987	100.0/0.0
Turkey/duck	279,719	7035	97.5/2.5
Poultry total	5,847,740	16,136	99.7/0.3
Breeding pigs	1300	13,637	8.7/91.3
Fattening pigs	21,811	195,059	10.1/89.9
Sows/piglets	1	36	2.7/97.3
Pig total	23,112	208,732	10.0/90.0
Breeding ewes ≥ 1 yr	28,082	74,787	27.3/72.7
Rams	1156	2257	33.9/66.1
Lambs	18,471	38,402	32.5/67.5
Sheep total	47,709	115,446	29.2/70.8
Grand total (all species)	6,135,461	1,047,314	85.4/14.6

Scenario A: 1% cattle/sheep manure, 46% pig manure, and 50% poultry litter. Scenario B: 8% cattle/sheep manure, 71% pig manure, and 50% poultry litter. † Percentages are based on Scenario A and Scenario B assumptions.

Table 2. Animal head numbers and manure production in Monaghan and Tipperary.

Animal Category	Monaghan Heads	Tipperary Heads	Monaghan/Tipperary Share (%) †
Dairy cows	38,100	182,500	17.3/82.7
Dry cows	31,100	53,600	36.7/63.3
Bulls	1700	3800	30.9/69.1
Cattle male ≥ 2 yr	11,200	47,600	19.0/81.0
Heifer ≥ 2 yr	14,300	29,500	32.6/67.4
Cattle male 1–2 yr	27,100	87,400	23.7/76.3
Heifer 1–2 yr	31,300	96,900	24.4/75.6
Male calf < 1 yr	30,300	102,100	22.9/77.1
Female calf < 1 yr	31,800	103,600	23.5/76.5
Cattle total	216,900	707,000	23.5/76.5
Laying birds	910,936	7809	99.2/0.8
Breeding birds	197,418	305	99.8/0.2
Broiler (table) birds	4,459,667	987	100.0/0.0
Turkey/duck	279,719	7035	97.5/2.5
Poultry total	5,847,740	16,136	99.7/0.3
Breeding pigs	1300	13,637	8.7/91.3
Fattening pigs	21,811	195,059	10.1/89.9
Sows/piglets	1	36	2.7/97.3
Pig total	23,112	208,732	10.0/90.0
Breeding ewes ≥ 1 yr	28,082	74,787	27.3/72.7
Rams	1156	2257	33.9/66.1
Lambs	18,471	38,402	32.5/67.5
Sheep total	47,709	115,446	29.2/70.8
Grand total (all species)	6,135,461	1,047,314	85.4/14.6

Scenario A: 1% cattle/sheep manure, 46% pig manure, and 50% poultry litter. Scenario B: 8% cattle/sheep manure, 71% pig manure, and 50% poultry litter. † Percentages are based on Scenario A and Scenario B assumptions.

Table 3 details the volume of manure available in Monaghan and Tipperary under business as usual (BAU) case (Scenario A) and a centralised co-operative scheme (Scenario B). While cattle may produce significantly more manure compared to other livestock, only the manure of livestock kept on wet liquid slurry systems can be included in resource estimates, as this resource can be easily collected [17]. A total of 1% of cattle manure compared to 46% of pig manure can be considered available as cattle are generally held outdoors, while pigs are generally housed indoors [17]. Even a small anaerobic digestion (AD) plant (~100 kWe) would require manure from over 1000 cows or 6000 pigs, making on-farm AD unfeasible. Developing a co-operative scheme with centralised hubs for biomass processing and encouraging co-digestion of feedstocks increases the amount of slurry that can be captured from smaller farms. In this scenario, cattle and pig manure available for processing rise to 8% and 71%, respectively [17]. The same assumptions for cattle manure are applied to sheep manure for calculations, as the average animals per farm is similar (Table S2).

Table 3. Manure available for valorisation in Monaghan and Tipperary.

	Scenario A: Monaghan	Scenario A: Tipperary	Scenario B: Monaghan	Scenario B: Tipperary
	Kt/Year	Kt/Year	Kt/Year	Kt/Year
Cattle manure	22.6	79.2	180.7	634.0
Poultry litter	3.1	0.03	3.1	0.03
Pig manure	16.2	16.2	25.1	225.9
Sheep manure	0.4	1.0	3.3	8.1
Total	42.4	96.5	212.2	868.1

Table 3. Manure available for valorisation in Monaghan and Tipperary.

	Scenario A: Monaghan	Scenario A: Tipperary	Scenario B: Monaghan	Scenario B: Tipperary
	Kt/Year	Kt/Year	Kt/Year	Kt/Year
Cattle manure	22.6	79.2	180.7	634.0
Poultry litter	3.1	0.03	3.1	0.03
Pig manure	16.2	16.2	25.1	225.9
Sheep manure	0.4	1.0	3.3	8.1
Total	42.4	96.5	212.2	868.1

Poultry litter has a different composition from livestock manure as it is a mixture of wood shavings, straw, poultry manure, urine, feathers, and food. Since it contains wood chips and straw, it is easier to transport as a bulk material. Broiler birds produce ten times less litter (0.002 m³ litter/bird) compared to laying birds (0.02 m³ litter/bird). According to ICT Biochain, 55% of poultry litter is used as mushroom compost, leaving 45% for land-spreading. It is assumed that 50% of this land-spread volume can be diverted to other uses, such as energy generation or other processing [17]. A Sankey diagram featuring this information is available in Supplementary Materials Figure S5. By moving to a co-operative scheme, nearly five times more manure is available in Monaghan and nine times in Tipperary. Cattle manure provides the highest amount of manure in each county, followed by pig manure, making these the best options for valorisation in a centralised hub scheme.

Figure 1 shows that while dairy cows produce the largest amount of manure compared to other animals, poultry litter contains the highest concentration of nutrients in kg/t manure (Figure 1). This may unlock potential technologies for valorisation of poultry litter at low quantities but high economic value. As an energy source, livestock manure has a low energy density due to its high moisture content, which averages at ~90% for cattle and pigs, and ~75% for sheep and poultry [16].

3.2. Crops and Horticulture

Table 4 details the hectares of land dedicated to crop growing in Monaghan and Tipperary as reported in the CSO 2010 Farm Survey. Tipperary has ~7 k more hectares of crop land compared to Monaghan. Monaghan is highly focused on mushroom production, while Tipperary crops are more varied in comparison. Mushrooms are a major industry in Monaghan, with over 22 k hectares dedicated to their growth. Value chains for the most common grown crops (wheat, barley, oat, rapeseed, and mushrooms) are illustrated in Supplementary Materials Figures S5–S10. The value chains show that the main waste output for barley, wheat, and oats is straw (Figures S5–S7). Roughly three tonnes of spent compost are generated for every tonne of mushrooms produced, and the entire cultivation process from substrate inoculation to first harvest usually takes about four weeks [18].

The fates of these biomass wastes are depicted in the Sankey diagram (Figure 2). Most of these biomass wastes are utilised, e.g., applied to land or used as animal bedding/feed. Between 62% and 97% barley, oat, and wheat straw is used for animal feed/bedding compared to 25% of winter rapeseed straw used for animal purposes. Over 90% of spent mushroom compost (SMC) and 100% of mushroom offcuts in Ireland are spread on land [19]. However, 10% or 7.3 kt/year SMC is unused, creating a clear opportunity for valorisation.

Table 4. Hectares of land dedicated to crops in Monaghan and Tipperary and the waste output for each crop type.

Crop	Monaghan	Tipperary	Biomass Wastes	Monaghan	Tipperary
	Hectares	Hectares		Tonnes	Tonnes
Winter wheat	2	3993	Winter wheat straw	8	16,771
Spring wheat	3	648	Spring wheat straw	9	1944
Winter barley	40	3651	Winter barley straw	168	15,334
Spring barley	265	10,951	Spring barley straw	954	39,424
Winter oats	0	1068	Winter oat straw	0	5020
Spring oats	18	645	Spring oat straw	70	2516
Oilseed rape	4	367	Winter oil rapeseed straw	22	2006
			Spring oil rapeseed straw	11	1003
Mushrooms	22,390	8176	Spent Mushroom compost	52,000	20,800
			Mushroom offcuts	2237	895

Table 4. Hectares of land dedicated to crops in Monaghan and Tipperary and the waste output for each crop type.

Crop	Monaghan	Tipperary	Biomass Wastes	Monaghan	Tipperary
	Hectares	Hectares		Tonnes	Tonnes
Winter wheat	2	3993	Winter wheat straw	8	16,771
Spring wheat	3	648	Spring wheat straw	9	1944
Winter barley	40	3651	Winter barley straw	168	15,334
Spring barley	265	10,951	Spring barley straw	954	39,424
Winter oats	0	1068	Winter oat straw	0	5020
Spring oats	18	645	Spring oat straw	70	2516
Oilseed rape	4	367	Winter oil rapeseed straw	22	2006
			Spring oil rapeseed straw	11	1003
Mushrooms	22,390	8176	Spent Mushroom compost	52,000	20,800
			Mushroom offcuts	2237	895

Table 5 shows that there is significant quantity of mushroom biomass available from just unused SMC or diverting 50% SMC from land application to other valorisation techniques. Since SMC varies seasonally effecting its suitability for land application, 50% of this biomass was assumed available for valorisation. A total of 50% of the mushroom offcuts were also assumed available for valorisation with the SMC.

Table 5. Crop/Horticulture biomass available for valorisation in Monaghan and Tipperary.

	Scenario A: Monaghan	Scenario A: Tipperary	Scenario B: Monaghan	Scenario B: Tipperary
	Kt/Year	Kt/Year	Kt/Year	Kt/Year
Unused SMC	5.2	2.1	5.2	2.1
SMC to land	23.4	9.4	23.4	9.4
Mushroom offcuts to land	1.1	0.4	1.1	0.4
Straw	0.04	3.8	0.07	7.4
Total	29.8	15.7	29.8	19.3

Scenario A: 100% unused SMC; 50% SMC to land; 50% mushroom offcuts to land; 50% straw available; Scenario B: 100% unused SMC; 50% SMC to land; 50% mushroom offcuts to land; 98% straw available.

Table 5. Crop/Horticulture biomass available for valorisation in Monaghan and Tipperary.

	Scenario A: Monaghan	Scenario A: Tipperary	Scenario B: Monaghan	Scenario B: Tipperary
	Kt/Year	Kt/Year	Kt/Year	Kt/Year
Unused SMC	5.2	2.1	5.2	2.1
SMC to land	23.4	9.4	23.4	9.4
Mushroom offcuts to land	1.1	0.4	1.1	0.4
Straw	0.04	3.8	0.07	7.4
Total	29.8	15.7	29.8	19.3

Scenario A: 100% unused SMC; 50% SMC to land; 50% mushroom offcuts to land; 50% straw available; Scenario B: 100% unused SMC; 50% SMC to land; 50% mushroom offcuts to land; 98% straw available.

In Ireland, straw is predominantly ploughed back into the field or used for animal bedding, this is due to its bulkiness and unsuitability for transport over large distances [17]. A total of 100% of spring rapeseed straw is ploughed back into land as shown in Figure 2. and is reflected in the simpler value chain for rapeseed compared to other crops (Figure S8) [19]. The amount of straw ploughed into the field depends on market value, weather/ground conditions, and storage capacity [17]. According to the SEAI, it can be assumed that a 2% minimum of straw is ploughed into the land, whatever the market/weather conditions, leaving 98% for valorisation (best-case scenario) [17]. A more realistic estimate is that 50% straw would need to be ploughed back into the land, leaving the other half for valorisation options. Previous estimates state that 1000 kt/year of straw is required for 7 million heads of cattle [20]. Calculating this for Monaghan and Tipperary cattle numbers provides a figure of 30 kt/year and 103 kt/year, respectively. However, according to ICT Biochain, 1.2 kt (Monaghan) and 71.2 kt (Tipperary) of straw are used for animal bedding and feed. This means that no straw can be diverted from the animal bedding/feed route for other valorisation options in these two counties. Therefore, the focus of available crop waste is on straw ploughed into the land.

Figures S11–S13 compare the available characteristics of crops as reported on the Phyllis biomass website. SMC contains a higher percentage of moisture content and higher major element concentration, but the lowest net calorific value when compared to straw samples. Rapeseed straw has a relatively high hemicellulose content, making it a good source for bioethanol production [21]. Straw and SMC have low–medium energy densities, making them unsuitable for energy generation using standard processes (see Figure S12) [17].

3.3. Forestry

Forestry extent differs sharply between the counties: Monaghan has 4810 ha of forest vs. 43,860 ha in Tipperary (almost ten times more land dedicated). Conifers dominate in Monaghan (55%; 2650 ha) and 72% (31,680) in Tipperary with Sitka Spruce, the principle species (1700 ha Monaghan; 20,740 ha Tipperary) [22]. Broadleaves account for 2160 ha in Monaghan and 12,130 ha in Tipperary. This means that Tipperary is slightly above the national average with a forest coverage of 12%, compared to 5% forest coverage in Monaghan [22]. Sitka Spruce is the most common conifer grown in Ireland [22]. This species mix underpins the value chain fates in Figure 3, stating conifer-rich Tipperary feeds stronger board mill flows, while a larger share of broadleaf material is returned to land or used for energy.

Figure S14 in Supplementary Materials shows the conventional value chain associated with the forestry industry in Ireland. Forestry wastes have a more varied use compared to animal and crop wastes, depending on the tree species. Tipperary supplies almost nine-tenths of the forestry residues (Figure 3). Board mills already capture 53% (~49 kt yr⁻¹), leaving 47% (~43 kt yr⁻¹) technically available for further valorisation. Material now routed to land (20%) or on-site energy (16%) totals 13.8 kt yr⁻¹ and constitutes the “available for valorisation” stream hereafter. The Sankey diagram of the fate of Monaghan and Tipperary forestry biomasses as calculated from the ICT Biochain project. The most common fate for spruce, pine, and other conifers is board mills, where they undergo processing into further products, e.g., pallets, stakes, etc. Broadleaf tree wastes are predominantly returned to land (60%) or used for energy generation (40%).

It is assumed that 50% of biomass used for energy generation can be diverted to an additional cascading system of valorisation, i.e., valorise these biomasses before generating energy. In Ireland, the tops of trees (tip-7 cm), branches, and stumps are generally left in the forest after clearfelling, which refers to the land portion of the Sankey diagram [23]. According to ICT Biochain, between 20 and 60% of biomass is fated for land depending on the tree type. Due to environmental constraints and soil type, gathering of biomass from the forest floor may be achievable on only 35% of forest harvest sites in Ireland [23]. Another method of calculating this is to use Coillte data for tip-7 cm tree diameter. Using the same 35% harvesting of forest sites, calculates a potential valorisation figure of 0.9 kt for Monaghan and 4.3 kt for Tipperary. However, this Coillte estimate does not take tree branches into account. Taking into consideration the deficit in animal bedding material described in Section 3.2, it is assumed that no forestry biomass could be diverted from this use. Stake and board are also not included in calculations as they have definite high-value valorisation options. Table 6 therefore details the amount of forestry biomass available for valorisation in counties Monaghan and Tipperary.

Table 6. Forestry biomass available for valorisation in Monaghan and Tipperary.

	Monaghan	Tipperary
	Kt	Kt
Forestry biomass to land	0.5	6.0
Forestry biomass to energy	0.5	6.8
Total	1.0	12.8

Table 6. Forestry biomass available for valorisation in Monaghan and Tipperary.

	Monaghan	Tipperary
	Kt	Kt
Forestry biomass to land	0.5	6.0
Forestry biomass to energy	0.5	6.8
Total	1.0	12.8

Figures S15–S17 show the differences between the most common tree species in Ireland. Spruce and larch have the highest moisture contents of the tree species and the lowest gross and net calorific values, meaning that these two tree species are suited to other valorisation options rather than for energy generation. Figure S17 shows the major element analysis of the bark of different tree species. Calcium is the highest major element existing in the bark of each tree species. This poses an interesting area to focus valorisation efforts.

3.4. Stakeholder Analysis

Two sequential workshops with regional actors in Monaghan and Tipperary revealed both enthusiasm and caution towards on-site biowaste valorisation. Workshop 1 identified eight cross-cutting barriers and opportunities. Workshop 2 tested two cascading technology chains and confirmed that market certainty is the decisive factor for adoption. A power–interest appraisal grouped participants into six salient stakeholder clusters, highlighting which actors can most effectively unlock or obstruct specific issues.

3.4.1. Workshop 1: Mapping Barriers and Opportunities

The first stakeholder workshop, held in Monaghan and Tipperary explored four themes, i.e., Market, Feedstocks, Logistics, and Knowledge/Communication, that are common themes for bioeconomy transition studies [24,25]. Each of the participants spent equal time at every table, ensuring balanced exposure across topics.

Coding of the mind-maps (Figure 4; yellow = barriers, green = opportunities) produced eight recurrent, cross-cutting issues. They are as follows: (i) communication to link dispersed actors; (ii) dissemination of technical and market knowledge; (iii) local/rural development and cooperation; (iv) legislation and regulation; (v) incentives and funding mechanisms; (vi) capital and operational costs; (vii) perception of waste as resource vs. liability; and (viii) feedstock characteristics and separation requirements. These issues echo findings from other European waste-valorisation initiatives that highlight knowledge gaps, regulatory complexity, and market immaturity as dominant constraints [26].

3.4.2. Stakeholder Clusters and Salience Assessment

Following Bryson’s (2004) [27] recommendation to aggregate actors with similar institutional roles and concerns, we applied a coding-and-clustering procedure to the Workshop 1 findings. The resulting six clusters are summarised in Table 7, using the classic power–interest grid nomenclature.

Table 7. Primary stakeholder clusters and their salience.

Cluster	Typical Organisations	Power *	Interest *	Salient Issues
Primary producers	Dairy and poultry farmers, forestry owners, hemp growers	●●○	●●●	Haulage cost, fertiliser offsets, CAP funding
Waste management and logistics firms	Hauliers, co-ops, circular-hub start-ups	●●●	●●○	Transport incentives, grid connection, traffic planning
Technology and service providers	AD developers, pyrolysis vendors, engineering consultants	●●○	●●●	Feedstock spec, finance, permits
Local authorities and regulators	County councils, EPA, planning boards	●●●	●●○	Licensing, zoning, community acceptance
Financiers and policy makers	SEAI, LEADER, local enterprise offices	●●●	●●○	Grants, tariffs, rural development
Civil society and knowledge brokers	Teagasc, academia, NGOs, farming unions	●○○	●●●	Demonstration sites, outreach, “green agenda”

* Power: ability to block or enable a pathway; Interest: level of concern with valorisation outcome (● = low, ●● = medium, ●●● = high).

Table 7. Primary stakeholder clusters and their salience.

Cluster	Typical Organisations	Power *	Interest *	Salient Issues
Primary producers	Dairy and poultry farmers, forestry owners, hemp growers	●●○	●●●	Haulage cost, fertiliser offsets, CAP funding
Waste management and logistics firms	Hauliers, co-ops, circular-hub start-ups	●●●	●●○	Transport incentives, grid connection, traffic planning
Technology and service providers	AD developers, pyrolysis vendors, engineering consultants	●●○	●●●	Feedstock spec, finance, permits
Local authorities and regulators	County councils, EPA, planning boards	●●●	●●○	Licensing, zoning, community acceptance
Financiers and policy makers	SEAI, LEADER, local enterprise offices	●●●	●●○	Grants, tariffs, rural development
Civil society and knowledge brokers	Teagasc, academia, NGOs, farming unions	●○○	●●●	Demonstration sites, outreach, “green agenda”

* Power: ability to block or enable a pathway; Interest: level of concern with valorisation outcome (● = low, ●● = medium, ●●● = high).

In Table 7, “Power” denotes a cluster’s capacity to enable (e.g., approve permits, release funds) or block (e.g., deny licences, mobilise opposition) valorisation projects, whereas “Interest” captures the degree to which the cluster’s own objectives hinge on project success [28,29]. The rows are equal to clusters. Each row aggregates actors that share both an institutional role and a similar pattern of concerns in the coded data. The power column is a visual shorthand of the cluster’s ability to enable (e.g., approve permits, release funds) or block (e.g., deny licences, mobilise opposition) valorisation projects. “●●●” denotes a cluster routinely identified by itself and by others as decisive. The interest column reflects how strongly the cluster’s own objectives are tied to biomass valorisation success. “●●●” indicates direct economic stakes; “●” signals peripheral concern. The salient issues mention topics that are most frequently mentioned by that cluster and possess above-average centrality in the issue-theme network.

3.4.3. Workshop 2: Stress-Testing Cascading Technology Chains

Workshop 2 (“Potential New Technologies in the Bioeconomy”) was delivered online, and participants each belonged to at least one of the six clusters identified above. Two cascading technology chains are presented:

• Chain A: manures/poultry litter → anaerobic digestion → pyrolysis → [downstream steps] (Figure S18);
• Chain B: forestry and crop residues/spent mushroom compost (SMC) → [technology steps] (Figure S19).

Cascading use of biomass is promoted as a pillar of the circular bioeconomy because it extracts sequential value before final energy recovery [30,31]. Polling questions assessed perceived technological feasibility, market demand, and consumer acceptance.

Key quantitative results are as follows:

• Biogas emerged as the most desirable output (4.6 ± 0.4), reflecting Ireland’s established renewable-gas market infrastructure [32].
• Biochar and digestate attracted medium to high interest (≥4.0), driven by fertiliser-offset potential and soil-health narratives [33].
• Operational inter-dependency was flagged as a vulnerability: if any unit in the cascade fails, feedstock back-logs accrue, incurring storage costs, which is a risk observed in other cascade pilots [34].

3.4.4. Synthesis and Implications for the Project

Across both workshops, participants expressed a clear appetite for valorising on-site biowastes provided that end-product markets are demonstrably robust and regulatory pathways are transparent. This aligns with recent empirical work showing that perceived market risk is the primary adoption barrier for emerging bio-based value chains [24]. The power–interest matrix (Table 7) indicates who is best positioned to tackle each barrier. For example, Local authorities and regulators (high power, medium interest) are pivotal for streamlining licences and zoning, whereas civil society and knowledge brokers (low power, high interest) excel at outreach to improve waste perception. Targeted engagement with these clusters will therefore underpin forthcoming work packages on technology piloting and policy advocacy.

3.5. Cascading Technology Options

A reduced cascade was proposed, which incorporates AD (Figure 5) and pyrolysis (Figure 6) technologies only. Pyrolysis and AD are well-established technologies in Europe; they are relatively easy to operate, and the CAPEX and OPEX are reasonable compared to other technologies. Commercial fast-pyrolysis plants such as Empyro (25 kt yr⁻¹, Netherlands) and Fortum Joensuu (50 kt yr⁻¹, Finland) demonstrate technology-readiness levels of 8–9, and recent reviews confirm the technical maturity and economic competitiveness of biomass pyrolysis [35]. These technologies can be placed in a cascade in either order, depending on the location or product most desired. Solid digestate from AD can be used in pyrolysis to produce energy. In contrast, biochar from pyrolysis can be fed into AD to increase biogas production. A cascading use of biomass is promoted in many bioeconomy strategies alongside prioritising food production, prevention of land-use conflicts, and consideration of environmental and socio-economic impacts [36].

4. Discussion

To assess the circular bioeconomy potential in Monaghan and Tipperary, this study quantified biomass wastes from livestock, crops/horticulture, and forestry under a conventional Business as Usual (BAU) baseline and a Best-Case Co-operative scenario (BCS). Local stakeholder interviews (Supplementary Materials Interview S1) indicated that little biomass is actually regarded as “waste” in existing meat production chains, since most animal by-products are already rendered or reused. Instead, nutrient-rich manures and the spent mushroom compost (SMC) from mushroom farming emerged as the most pressing surplus biomass issues, along with some underutilised straw and forestry residues. Forestry contributions were relatively minor in Monaghan (a county with low forest cover), whereas Tipperary, blessed with larger dairy farms, tillage, and forest areas, showed greater overall biomass availability, especially when cooperation improves collection (Figure 7).

The co-operative scenario (BCS) yields a substantial increase in usable biomass (notably livestock manures in Tipperary), highlighting the impact of collective waste management efforts. The BAU Scenario A yields only modest quantities of recoverable biomass in both counties, as much of it remains used or unmanaged on individual farms. In contrast, Scenario B demonstrates that coordinated efforts (e.g., shared collection and processing facilities) could dramatically increase the mobilisation of agricultural residues, most noticeably in Tipperary, where livestock manures dominate the potential resource (Table 8). This reinforces that unlocking biomass for valorisation will depend on organisational models as much as on the technical availability of feedstocks.

Table 8. Percentages of each biomass waste assumed available for recovery under Business as Usual and Best-Case Co-operative scenarios.

	Scenario A: Business As Usual	Scenario B: Best-Case Co-Operative
Cattle/sheep manure	1%	8%
Pig manure	46%	71%
Poultry litter	50%	50%
Unused SMC	100%	100%
SMC to land	50%	50%
Mushroom offcuts to land	50%	50%
Straw	50%	98%
Forest biomass to land	35%	35%
Forest biomass to energy	50%	50%

Table 8. Percentages of each biomass waste assumed available for recovery under Business as Usual and Best-Case Co-operative scenarios.

	Scenario A: Business As Usual	Scenario B: Best-Case Co-Operative
Cattle/sheep manure	1%	8%
Pig manure	46%	71%
Poultry litter	50%	50%
Unused SMC	100%	100%
SMC to land	50%	50%
Mushroom offcuts to land	50%	50%
Straw	50%	98%
Forest biomass to land	35%	35%
Forest biomass to energy	50%	50%

4.1. Livestock and Poultry Biomass

Manure availability and nutrient management: Livestock agriculture generates large quantities of manure (slurries from cattle and pigs, and litter from poultry), which farmers traditionally spread on land as organic fertiliser. Stakeholders in both counties emphasised that animal manures are not “waste” per se but a valuable nutrient source; however, they acknowledged challenges in managing these nutrients within environmental limits. Ireland’s entire territory is designated as a Nitrates Directive vulnerable zone, meaning regulations cap manure applications at 170 kg N/ha to protect water quality [37]. In practice, intensive farming areas often face nutrient surpluses, and stakeholders noted that exporting or further processing manure might be necessary to avoid breaching these limits. In practice, slurry from housed cattle and pigs is stored 16–22 weeks over the closed-spreading season (Oct → Jan) as required by S.I. 113/2022, while poultry litter is produced year-round but stockpiled under cover until land-spread post-harvest. More than 70% of slurry therefore arises between November and March, creating a seasonal storage pinch-point [38]. This presents a trade-off, i.e., land application recycles nutrients and organic matter locally, but excess spreading can contribute to water pollution and greenhouse gas emissions, whereas off-farm valorisation can alleviate local nutrient overloads.

Land-spreading vs. valorisation trade-offs: Aligning manure management with climate and policy goals is a key discussion point. Agriculture accounts for about one-third of Ireland’s GHG emissions, a share poised to grow with Food Wise 2025 plans for increased output [39]. Simply spreading raw slurry can lead to methane and nitrous oxide emissions; by contrast, deploying waste-to-energy technologies can mitigate these. Current practice is splash-plate or trailing-shoe application once ground conditions permit. Agitation prior to spreading can release significant NH₃ and CH₄, a driver behind covered-storage and low-emission spreading rules introduced in 2023 [40]. For example, anaerobic digestion (AD) is highlighted as a win–win solution that captures biogas from manure and produces a nutrient-rich digestate fertiliser. Using AD, farms can convert manure “waste” into renewable energy while still returning stabilised nutrients to soil, thus supporting “smart” climate-friendly agriculture. Studies note that digesting manure avoids uncontrolled decomposition emissions and yields biofertiliser; in fact, it is preferable to spread digestate rather than raw slurry, to reduce carbon leaching and pathogen spread [41]. Composting of solid manures or poultry litter is another option to stabilise nutrients and reduce odours, though it does not produce energy. Stakeholders generally viewed these technologies positively for helping meet Ireland’s ambitious climate targets (51% emissions reduction by 2030) [37] and compliance with EU nutrient directives, but raised practical concerns. It was stressed that any valorisation must preserve fertiliser value, echoing the EU principle that nutrient recycling (returning N, P, K to land) should not be compromised even as energy is extracted.

Relevance to policy and technology uptake: In the context of national climate commitments and EU directives, valorising livestock biomass has significant appeal. Ireland’s Climate Action Plan and Ag-Climatise strategy promote on-farm AD as a way to cut agricultural emissions and produce biomethane fuel [42]. Similarly, the EU’s circular economy policies encourage treating manure not as waste but as a resource to be managed safely and efficiently. The challenge is implementation on the ground. Local stakeholders pointed out regulatory hurdles (e.g., permits under animal by-product rules for transporting manure to a digester) and the need for collective investment to make facilities viable. In the BCS scenario, farmers might cooperate via a shared AD plant or composting centre, an approach that the European Biogas Association also recommends to harness economies of scale. Stakeholders also flagged the need to secure Animal-By-Product transport permits (EC 1069/2009) [43] and an Industrial Emissions licence for digesters > 50 kWe, both of which can extend project lead-times to 12–18 months [44]. Overall, the discussion around livestock residues centres on balancing their agronomic value against environmental harms. With appropriate technology deployment, such as covered slurry storage, bioenergy production, and advanced nutrient management, manure from poultry, pigs, and cattle can be transformed from a diffuse emissions source into a feedstock for Ireland’s bioeconomy, contributing to renewable energy targets and improved nutrient stewardship [37].

4.2. Crop and Horticultural Biomass

Straw use and energy trade-offs: Crop-derived residues in these counties primarily consist of cereal straw and other plant matter from tillage farms. Under BAU, much of the straw is already utilised, where farmers either sell it for livestock feed and bedding or plough it back into soils to maintain soil organic carbon. Stakeholders noted that straw is only a “waste” in years of surplus; more often, it is a valuable commodity, so diverting it to bioenergy must be carefully evaluated. Using straw for combustion or biofuel production could displace its role as cattle fodder or as a soil conditioner. Removing too much straw can also deprive fields of organic matter and nutrients. Thus, there is a balance to strike between using straw in the bioeconomy vs. preserving its function in current farming systems [45]. Seasonality is another factor; straw is available mainly at harvest, requiring storage and coordinated collection if it were to feed a bioenergy plant year-round. Any valorisation strategy must align with agronomic cycles and ensure farmers are not left short of bedding material in winter. On the policy side, the EU promotes agricultural residue use for energy (straw is even listed as an advanced biofuel feedstock under RED II), yet policies like Ireland’s Straw Incorporation Measure (which incentivises tillage farmers to plough straw into soil for climate benefits) illustrate the competing objectives. Effectively, circular bioeconomy initiatives must work within these practical and policy constraints, finding win–win solutions where only genuinely excess straw is tapped for energy.

Mushroom compost and horticulture residues: Monaghan’s intensive mushroom industry produces a significant by-product stream in the form of spent mushroom compost (SMC). After several crop cycles, mushroom substrate (a mixture initially rich in straw and poultry manure) becomes “spent” and must be removed from production houses. An estimated ~3 t of SMC are generated per tonne of mushrooms produced [45], making SMC management a critical issue. At present, some SMC is land-spread as a liming fertiliser or sold to gardeners, but stakeholders reported that the local land capacity to absorb SMC is limited due to nutrient (especially phosphorus) saturation. Indeed, studies have long noted “competition for spread lands” among intensive enterprises in Ireland, too many organic wastes chasing limited available farmland for manure/compost application [46]. This means alternative SMC valorisation pathways are highly desirable. Options under discussion include using SMC as a feedstock for energy or new products. However, SMC has a high moisture content and is partially degraded, so its energy value is modest; direct combustion or anaerobic digestion of SMC can be technically challenging without pre-treatment or co-feeding with higher energy materials. More promising is the development of value-added products from SMC. The EU-funded BIOrescue project, for example, demonstrated that used mushroom compost can be converted into bio-based products like biodegradable crop protection agents [45]. Similarly, other pilots have explored processing SMC into pelletised organic fertilisers or soil amendments, creating marketable outputs while solving a waste problem. Stakeholders in the mushroom sector appear open to such innovation; they have a strong incentive to find sustainable outlets for SMC, especially as landfilling organic waste is increasingly restricted and costly [45]. Besides SMC, other horticultural residues (e.g., vegetable trimmings or unsold produce) were comparatively minor in the study areas, but the general principles apply: these residues could either be returned to soil or redirected into products like animal feed, compost, or bioenergy, depending on what yields the best economic and environmental outcome.

Policy context and willingness to diversify: The discussion around crop and horticulture residues ties into broader Irish and EU bioeconomy policy goals. The EU Circular Economy Action Plan and Bioeconomy Strategy call for maximising the use of agricultural side-streams, turning “waste into value” to reduce overall waste volumes [45]. In Ireland, circular bioeconomy initiatives emphasise that such residues should be utilised in a way that does not undermine soil health or existing agricultural uses [45]. This requires careful regional planning: for instance, in regions like Monaghan, encouraging a co-operative SMC processing facility could relieve local environmental pressures, while in Tipperary, straw-to-energy projects might only proceed if they do not create shortages for local farms. The interviews suggested stakeholders are cautiously willing to diversify uses of crop residues if supported by evidence and incentives. Many farmers are pragmatic—if a new market for their “leftovers” like straw or SMC offers better returns or solves a disposal headache, they will engage, provided it does not jeopardise their primary business. Therefore, policy frameworks (e.g., waste classification rules, grant supports for biomass supply chains, and knowledge transfer) will play a big role in whether crop and horticultural biomass is effectively mobilised beyond traditional practices [45]. The best-case scenario envisions mushroom growers, tillage farmers, and others collaborating in networks to supply feedstock to bio-based ventures, aligning with the EU’s vision of symbiosis between agriculture and industry where one sector’s residue becomes another’s raw material [45].

4.3. Forestry Residues

Current use and regional differences: Forestry-derived biomass played a relatively small role in Monaghan’s resource assessment but a more notable one in Tipperary, reflecting the counties’ contrasting forest cover. Monaghan has one of the lowest forest covers in Ireland, so its generation of forestry residues (harvesting brash, sawdust, offcuts) is minimal. Tipperary, on the other hand, has extensive forest plantations and sawmilling activity (including supply to wood panel factories), yielding a larger stream of low-grade wood that could be available for valorisation. Even so, the study found that forestry residues are quantitatively overshadowed by agricultural wastes in both counties. Crucially, much of the wood residue in Ireland is already utilised in some form. Nationally, about 40% of all wood fibre harvested is used for energy (e.g., wood chip for heat, sawmill residues for bioenergy) [47], and another significant share goes into wood-based panels and other products. This indicates a de facto cascading use: prime timber becomes lumber, while lower-grade biomass often goes to panel manufacturing or is burned for energy. Stakeholders in forestry and allied industries confirmed that little truly “goes to waste”; any sizeable forestry enterprise will either leave residue on the forest floor for soil nutrients or collect it for commercial use. In Tipperary, for instance, sawmills and board mills provide an existing outlet for tree tops, thinning, and sawdust. Thus, the additional recoverable forestry biomass in a co-operative scenario might come from improved mobilisation of currently underused resources (such as branch wood left in smaller private forests or roadside thinning) rather than from any large stockpile of unused waste.

Forestry expansion and valorisation pathways: Ireland’s climate and land-use policies foresee a major expansion in forestry over the coming decades, which could increase the volume of forest residues available in regions like Tipperary. As new forests mature, more biomass will become accessible for predominately bio-based products or energy, reinforcing the need to plan cascaded uses. In line with climate objectives, using wood sustainably can deliver multiple benefits: long-lived wood products lock away carbon, and residual biomass can substitute fossil fuels. However, stakeholders raised the point that simply burning all additional wood for energy would be a missed opportunity, exploring emerging technologies such as pyrolysis to convert forestry residues into biochar and biofuels or other high-value products. Pyrolysis (thermal decomposition of biomass in the absence of oxygen) can transform low-value woody waste into biochar, a carbon-rich material that can be used as a soil improver and carbon sequestration agent and simultaneously produce bio-oil/gas that can be used for energy. This approach aligns with both climate mitigation (since biochar sequesters carbon for the long term) and resource efficiency, extracting value beyond immediate combustion. Some workshop participants cited the example that producing biochar from forestry waste could help local farmers by providing a soil amendment while also creating carbon credits, illustrating the kind of cross-sector benefits a bioeconomy can yield. Additionally, using forestry residues for innovative bioproducts (for instance, bio-based chemicals, resins, or textiles) was mentioned as a longer-term possibility, though these markets are nascent in Ireland. The overall perspective is that forestry residues, while a smaller piece of the biomass puzzle in Monaghan and Tipperary, should be integrated into the regional bioeconomy strategy, ensuring that as Ireland’s forests grow, the hierarchy of uses is respected. High-quality wood should go to material uses first, and only the by-products and residual fractions should be diverted to energy or soil products, consistent with the EU cascading-use principle. This would mirror current practice where, for example, sawmill chips feed panel board factories and only surplus wood is used in energy generation [47].

Challenges and policy linkages: The discussion of forestry residues also surfaced logistical and policy challenges. Collecting small-diameter or dispersed woody material can be costly, and it was noted that in Monaghan, there is little incentive to gather brash from the county’s patchy woodlands at present. In Tipperary, existing biomass users (like wood energy plants) compete for resources, so any new valorisation project must secure a stable supply without inflating feedstock prices. This ties into national forestry and bioenergy policy: Ireland’s draft Forestry Programme and Climate Action Plan encourage more wood-based energy, but also emphasise efficient use of biomass in the bioeconomy. The EU Forest Strategy similarly promotes a “cascading” framework where wood contributes to the Green Deal targets in both materials and energy sectors. The best-case scenario envisions perhaps community-level initiatives such as a co-operative that collects forestry offcuts to produce biochar or pellets, which would complement existing industries. Aligning such efforts with Coillte (the state forestry agency) and private forest owners is crucial. By treating forestry by-products as a resource for high-value applications (like biochar for carbon farming or advanced biomaterials), the region can demonstrate innovative uses that go beyond the traditional firewood or mulch, thus adding a new dimension to the local bioeconomy.

4.4. Stakeholder Perspectives

An essential component of this study was the input from local stakeholders, consisting of farmers, agribusiness representatives, foresters, and community leaders, who provided on-the-ground perspectives about biomass utilisation. Their insights highlight practical considerations that any valorisation initiative must address:

Feedstock accessibility and consistency: Participants emphasised that securing a reliable supply of biomass is a fundamental hurdle. Farmers are generally protective of materials like manure and straw that have on-farm value, so convincing them to contribute these to a co-operative scheme would require trust and clear benefits. Seasonal and geographic variations also matter; for example, Tipperary’s larger dairy farms can supply cattle slurry year-round, whereas Monaghan’s poultry litter arises from many small units that are geographically scattered. Building a supply chain for feedstock means accounting for these differences and ensuring contributors that they can obtain nutrients or other benefits back when needed. A co-operative scenario would likely involve detailed agreements on feedstock quotas, scheduling of collections, and compensation (whether monetary or in the form of biofertiliser return).

Logistical and regulatory barriers: Stakeholders across both counties voiced concerns about the “nuts and bolts” of biomass collection. Transporting bulky, wet materials like manure or SMC can be costly and logistically complex. It requires tankers or specialised trucks, storage tanks, and careful timing to avoid spillage or odour issues. Without sufficient infrastructure (e.g., intermediate storage depots, efficient transport routes), a regional biomass scheme could falter [45]. Regulatory issues compound this: moving and processing farm wastes invokes various regulations (animal by-product rules, waste permits, planning permissions for facilities, etc.). For instance, an anaerobic digester taking off-farm wastes needs approval under the EU Animal By-Product Regulation 1069/2009, and spreading digestate or compost must still comply with Nitrates Regulations. Stakeholders noted that navigating this bureaucracy can deter projects unless there is administrative support or streamlining. Uncertainty over waste classification was another issue raised, as some materials might lose their “waste” label if processed (becoming a product), but inconsistent rules (national vs. EU) make planning difficult [45].

Trust in technology and market readiness: Many local actors had limited exposure to technologies like anaerobic digestion, pyrolysis, or advanced biorefineries, given that such facilities are not yet common in these counties. As a result, there was caution about the technical reliability and economic viability of proposed solutions. Farmers asked whether digesters or biochar units would definitely work as advertised and for the long term, or if they might end up with stranded assets. The “not in my backyard” sentiment was relatively low (most stakeholders were not opposed to bioenergy facilities in principle), but there was a clear preference for proven models. This suggests the need for pilot projects or demonstrations to build confidence. Additionally, market uncertainties, for example, who will buy the biogas, or whether there is a guaranteed market for biochar or compost outputs, were declared. Stakeholders want assurance that if they invest effort or capital into a co-operative venture, there will be a stable demand and revenue for the end products. Some pointed to fluctuating energy prices and policy incentives as a risk (e.g., changes in renewable energy tariffs or carbon credit values could affect project economics).

Attitudes toward co-operative models: The notion of a co-operative approach (as embodied in the BCS scenario) was met with cautious optimism. Many stakeholders see the logic: no single farmer or small business can alone justify the investment in a biorefinery or large-scale composter, but together they might. Successful precedents, such as farmer co-ops in the dairy sector, provide a template for collective action. Indeed, EU analysts recommend forming biomass supplier cooperatives to pool resources and overcome fragmentation in the bioeconomy [45]. However, stakeholders also warned that co-ops require strong governance and trust among members. Past experiences in collective initiatives (outside the bioenergy realm) have occasionally led to disputes, so roles, profit-sharing, and responsibilities would need to be clearly defined. The workshops surfaced a genuine interest in exploring a joint venture for biomass valorisation. This is to be paid attention to if external support (government grants or technical assistance) is available, but also a realisation that community buy-in must be built gradually. In Monaghan and Tipperary alike, champions or “local leaders” would likely be needed to push the co-operative idea forward and maintain momentum. Overall, the stakeholder analysis underscores that technical feasibility alone is not enough; social and organisational aspects are equally critical. Engaging stakeholders early, transparently addressing their concerns, and designing business models that equitably share benefits will determine whether a theoretical best-case scenario can become reality on the ground.

4.5. Cascading Technology Options

Bringing together the above threads, an overarching theme is the importance of matching each biomass type with the appropriate technology and use. This should be in line with the cascading-use principle championed by Irish and EU bioeconomy policy. Ireland’s National Policy Statement on the Bioeconomy explicitly endorses the cascading principle, meaning higher-value applications of biomass (such as food, feed, and bio-based materials) should be prioritised, and only after those opportunities are exhausted should biomass be used for energy [48]. In practical terms, this requires designing valorisation pathways that first consider if a residue can displace a raw material in the feed or food chain, or serve as a renewable material input, before simply burning or digesting it for energy. The “food/feed-fuel-function” hierarchy encapsulates this: society must balance using biomass for food/feed, for fuel/energy, and for ecosystem or soil functions.

Tailoring technologies to feedstock quality: The study’s findings suggest a menu of cascading technology options applicable to Monaghan and Tipperary’s biomass. Wet, nitrogen-rich feedstocks like animal slurries are best suited to anaerobic digestion, producing biogas (for energy) and digestate that returns nutrients to farms. This respects the cascade by extracting energy while still looping nutrients back into food production via soils. Drier lignocellulosic residues (straw, woody forestry offcuts) might bypass AD (which works poorly on such substrates) and instead go to thermochemical or material uses. For instance, clean straw could be used as an animal feed supplement or mushroom substrate input (a material use) before considering it for energy. If there is surplus straw that has no feed or bedding demand, it could then be combusted in a biomass boiler or processed into biofuels, steps lower in the cascade. Similarly, forestry woody residues should first be evaluated for any material value (e.g., wood chips for composite boards, or as mulch) and only the remaining fraction used in energy or char production. Spent mushroom compost, having already served a purpose in food cultivation, contains valuable organic matter and lime; the cascading approach would favour using it as a soil improver or fertiliser replacement (a functional use) over simply disposing of it. Only if those higher uses are saturated would it be possible to consider using SMC (in energy recovery (and even then, perhaps as a last-resort co-fuel in a biomass plant). By matching each feedstock to a technology appropriate to its composition, we ensure each resource is put to its highest and best use.

Aligning with policy and circular economy goals: Both the Irish national strategy and EU directives provide guidance that supports such a cascading deployment of technologies. The EU waste hierarchy and circular economy policies encourage recycling and recovery of materials before energy recovery. In agriculture, the EU’s emphasis on nutrient recycling (e.g., recent discussions on allowing RENURE recycled fertilisers from manure under the Nitrates Directive) shows a push to safely loop farm nutrients back to land rather than lose them in waste streams [45]. Ireland’s bioeconomy vision likewise integrates the food-first principle alongside cascade use [48], seeking to avoid resource competition between fuel and food. In practical terms, this means any new bioresource project in Monaghan or Tipperary should demonstrate that it is not diverting biomass from an existing critical use (like animal feed or soil fertility) to a lower-value use. Instead, projects should capitalise on genuine waste or underused material. This approach echoes the EU’s cascading-use principle in forestry and beyond: use biomass sequentially for products and only lastly for energy [45].

Synergies and trade-offs: Adopting a cascading framework helps identify synergies between food, feed, fuel, and ecosystem functions. For instance, deploying AD for dairy farm slurries can reduce emissions (fuel output) while improving fertiliser management (soil function), without sacrificing any food production. A synergy that advances climate goals and farming sustainability simultaneously. On the other hand, trade-offs do arise. Diverting a portion of straw to energy might marginally reduce the bedding available locally, requiring adjustments or imports in a bad year. Using manure in a central digester means farmers must manage the logistics of returning digestate or finding alternative fertilisers. These trade-offs must be transparently weighed. The cascading principle does not mean no biomass can ever be used for energy; rather, it ensures that when biomass is used for energy or fuel, it is performed in a way that does not foreclose higher uses or undermine environmental health. In Monaghan and Tipperary, a cascading strategy might involve a portfolio of technologies: farm-scale and centralised digesters for manures, composting units for SMC and other organic fines, and perhaps pyrolysis units for woody residues. Each application is chosen to suit the feedstock and positioned at the appropriate level of the hierarchy. Such a strategy aligns with Ireland’s National Bioeconomy Policy by putting the economy on a more sustainable footing through efficient resource use, and it operationalises EU principles by creating integrated value chains. By doing so, regions like Monaghan and Tipperary can serve as exemplars of how to cascade biomass use, extracting energy and products from “wastes” while reinforcing, not detracting from, core agricultural and environmental functions [45,48].

5. Conclusions

This research has shown there is a significant amount of biomass wastes, which can be gathered for valorisation without obstructing current uses. Two scenarios were developed to illustrate the difference in collectable quantities of biomass wastes in counties Monaghan and Tipperary: Business as Usual (Scenario A) and Best-Case Co-operative (Scenario B). The Best-Case Co-operative model assumes that more biomass wastes can be gathered and a co-operative system utilised to increase feedstock quantities for valorisation technologies. In Monaghan, 73 t of biomass waste vs. 240 t are potentially available for valorisation under Scenario A vs. Scenario B, respectively. This is approximately a 3-fold increase. In contrast, in Tipperary, a 7-fold increase in biomass waste is achieved, comparing Scenario A (126 t) against Scenario B (905 t). The majority of the increase comes from collecting more manure under a co-operative model, and the large focus of Tipperary on livestock and poultry farming. This highlights the importance of engaging local stakeholders to build co-operative models of biomass use. Not only is this environmentally beneficial, but also socially and economically advantageous. The research identifies that although animal by-products are largely being processed into high-value products, manure management presents both challenges and opportunities. It also highlights that the majority of cereal straw is repurposed for animal bedding and feed, yet a notable fraction remains unused. Particularly, SMC and mushroom offcuts present significant opportunities for valorisation. The forestry sector contributes a considerable amount of residual biomass, including sawdust and offcuts. While some of this biomass is utilised for energy production, there is potential to enhance its value through advanced technologies like pyrolysis, producing biochar and syngas. The integration of stakeholder perspectives reveals a consensus on the necessity for supportive policies, financial incentives, and knowledge-sharing platforms to facilitate the adoption of biomass valorisation technologies. The cascading-use principle, as advocated in Ireland’s National Policy Statement on the Bioeconomy, should guide the prioritisation of biomass applications, ensuring that higher-value uses are explored before energy recovery. Thus, the valorisation of biomass wastes in Monaghan and Tipperary presents a multifaceted opportunity to enhance environmental sustainability, contribute to renewable energy goals, and stimulate rural economies. Realising this potential requires a collaborative approach involving stakeholders across the value chain, supportive policy frameworks, and investment in appropriate technologies.