Industrial Food Waste Screening in Emilia-Romagna and the Conceptual Design of a Novel Process for Biomethane Production

Abstract

The REPowerEU plan is aimed at a target of 35 bcm of biomethane annually by 2030, up from 4 bcm in 2023, requiring about EUR 37 billion in investment. Food waste is identified as a key feedstock, characterized by discrete homogeneity, although its availability may vary seasonally. In Italy, the Emilia-Romagna region generates approximately 450 kt/y of industrial waste from the food and beverage sector, primarily originating from meat processing (NACE 10.1), fruit and vegetable processing (NACE 10.3), and the manufacture of vegetable and animal oils and fats (NACE 10.4). Of this amount, food and beverage processing waste (EWC 02) accounts for about 302 kt from NACE 10 (food, year 2019) and 14 kt from NACE 11 (beverage, year 2019). This study provides a comprehensive screening of waste streams generated by the local food and beverage industry in Emilia-Romagna, evaluating the number of enterprises, their value added, and recorded waste production. The screening led to the identification of suitable streams for further valorization strategies: a total of ~93 kt/y was selected for the preliminary conceptual design of an integrated process combining anaerobic digestion with hydrothermal treatment, aimed at supporting national biomethane production targets while maximizing material recovery through hydrochar production. Preliminary estimations indicate that the proposed process may achieve a biochemical methane potential of approximately 0.23 Nm³/kg_VS, along with a hydrochar yield of about 130 kg/t_waste.

1. Introduction

According to the United Nations Food and Agriculture Organization (FAO), approximately one-third of all food produced is lost during harvesting and throughout the supply chain, resulting in an estimated annual loss of USD 1 trillion [1,2]. Beyond its economic consequences, food waste is a significant source of greenhouse gas emissions, water loss, air and water pollution, biodiversity decline, soil degradation, and climate change [1].

In Europe, about 30 Mt of inedible food waste is produced at the food manufacturing stage, showing the potential to be further employed for waste-to-value processes given their high level of homogeneity [3]. This characteristic is fostering the use of food waste generated by the food processing industry as a feedstock in biorefineries, seeking to enable zero-waste production and promote a circular economy approach by transforming residues into valuable raw materials upon the reliable and continuous availability of the selected biomass [3,4]. These advancements play a pivotal role in supporting the implementation of key EU policy frameworks, including the Bioeconomy Strategy [5] and the Circular Economy Action Plan [6].

Among the strategies to substitute fossil fuel accelerating Europe’s clean energy transition, the Repower EU plan aims at scaling up sustainable biomethane yearly production from roughly 4 bcm in 2023 to 35 bcm by 2030 [7], reducing EU gas dependence with an estimated EUR 37 billion investment [8]. The Biomethane Action Plan drafted by the EU Commission outlines the necessity to overcome production barriers hindering sustainable paths for biomethane production based on waste generated by different economic sectors such as agricultural and agro-industry waste and residues, forest industry waste and residues, food industry waste, energy and chemical industry biogenic CO₂ effluents and waste, industrial wastewater, and domestic organic waste [8,9,10].

Strategies for food waste valorization play a significant role in the Emilia-Romagna region located in northern Italy. This area is distinguished by a highly developed food and beverage industry, generating over EUR 4.1 billion in value added [11]. A variety of food waste streams can be detected, whose current fate mainly consists of energy recovery or other disposal operations (D2 to D14 as from 2008/98/EC Annex 1 [12]). The present paper aims at providing a screening of the industrial food waste streams in Emilia-Romagna (Section 3), identifying suitable feedstocks for biomethane production through anaerobic digestion (Section 4.1). Moreover, a preliminary conceptual design of a novel process combining anaerobic digestion with hydrothermal treatment is proposed (Section 4.2) and delivered for future sizing and performance estimation works.

2. Approach and Methodology

2.1. Screening of Food Waste Production in Emilia-Romagna Region

The analysis of waste streams generated in Emilia-Romagna is based on publicly available data from authoritative sources and relies on three key indicators: the number of enterprises, waste production, and value added.

Data on the number of enterprises operating in the Emilia-Romagna food and beverage industry were retrieved from ISTAT (Istituto Nazionale di Statistica) with reference to Archivio Statistico delle Imprese Attive (ASIA). The companies were classified based on the Statistical Classification of Economic Activities in the European Community (NACE) [13] and grouped by provinces. As reported in

Table 1. Divisions 10 and 11 from NACE section C (Manufacturing) considered within the present study to collect data from the food and beverage industry [13].

Section C—Manufacturing
Division 10—Manufacture of Food Products
Group	Class	Title
10.1	Processing and preserving of meat and production of meat products
	10.11	Processing and preserving of meat
	10.12	Processing and preserving of poultry meat
	10.13	Production of meat and poultry meat products
10.2	Processing and preserving of fish, crustaceans and mollusks
	10.20	Processing and preserving of fish, crustaceans and mollusks
10.3	Processing and preserving of fruit and vegetables
	10.31	Processing and preserving of potatoes
	10.32	Manufacture of fruit and vegetable juice
	10.39	Other processing and preserving of fruit and vegetables
10.4	Manufacture of vegetable and animal oils and fats
	10.41	Manufacture of oils and fats
	10.42	Manufacture of margarine and similar edible fats
10.5	Manufacture of dairy products
	10.51	Operation of dairies and cheese making
	10.52	Manufacture of ice cream
10.6	Manufacture of grain mill products, starches and starch products
	10.61	Manufacture of grain mill products
	10.62	Manufacture of starches and starch products
10.7	Manufacture of bakery and farinaceous products
	10.71	Manufacture of bread; manufacture of fresh pastry goods and cakes
	10.72	Manufacture of rusks and biscuits; manufacture of preserved pastry goods and cakes
	10.73	Manufacture of macaroni, noodles, couscous and similar farinaceous products
10.8	Manufacture of other food products
	10.81	Manufacture of sugar
	10.82	Manufacture of cocoa, chocolate and sugar confectionery
	10.83	Processing of tea and coffee
	10.84	Manufacture of condiments and seasonings
	10.85	Manufacture of prepared meals and dishes
	10.86	Manufacture of homogenized food preparations and dietetic food
	10.89	Manufacture of other food products not elsewhere classified
10.9	Manufacture of prepared animal feeds
	10.91	Manufacture of prepared feeds for farm animals
	10.92	Manufacture of prepared pet foods
Division 11—Manufacture of beverages
Group	Class	Title
11.0	Manufacture of beverages
	11.01	Distilling, rectifying and blending of spirits
	11.02	Manufacture of wine from grape
	11.03	Manufacture of cider and other fruit wines
	11.04	Manufacture of other non-distilled fermented beverages
	11.05	Manufacture of beer
	11.06	Manufacture of malt
	11.07	Manufacture of soft drinks; production of mineral waters and other bottled waters

, the analysis considered divisions 10 and 11 from NACE section C (Manufacturing) in order to limit the screening to the food and beverage industry.

Waste production from the food and beverage industry at the national level was tracked based on the 2019 database from the Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA) [14]; meanwhile, the analysis at the regional level relied on data from Agenzia Regionale per la Prevenzione, l’Ambiente e l’Energia Emilia-Romagna (ARPAE) with reference to the special waste dataset [15] and the selected NACE codes. Moreover, waste classification is based on the European Waste Catalogue (EWC) [16], which is divided into 20 chapters (from 01 to 20). The chapter of interest for the present study is 02, i.e., waste from agriculture, horticulture, aquaculture, forestry, hunting and fishing, food preparation, and processing.

The data cleaning process used to identify the waste amount in Emilia-Romagna, its characterization, and regional distribution required a dual search filter, initially based on the waste’s origin and then on its nature. In the first step, only streams that originated from the food and beverage industry were selected with reference to the NACE codes as selection criteria (refer to Table 1). Following this step, the EWC code was employed to ensure that only organic waste is considered, eliminating plastics, metals, and other waste flows in the initial screening, as they were not relevant to the current study.

Data concerning food and beverage waste streams are referred to the year 2019 and were retrieved and analyzed in terms of evaluating the contribution of the selected waste production at the regional (i.e., Emilia-Romagna) and national levels.

The third indicator considered for screening is the value added, representing the growth of the economic system in terms of new goods and services made available to the community for final use. According to ISTAT, the value added is calculated as the difference between the value of goods and services produced by individual production sectors and the value of intermediate goods and services they consume (such as raw materials, auxiliary inputs, and services from other units) [17]. The selection of suitable waste streams to be further investigated in terms of composition and potential for advanced valorization processes was carried out based on both the amount of waste produced per NACE group and its relative impact with respect to the value added of the producers.

A summary of the aforementioned adopted methodology is graphically represented in Figure 1.

2.2. Conceptual Design of Alternative Waste-to-Value Process

The waste streams of interest selected from the regional waste produced from the industrial food and beverage industry were divided into solids and sludges. Their characterization was carried out in terms of solid fraction, volatile solids, ashes, and moisture, as well as carbohydrates, proteins, and lipids, based on literature data.

Considering the organic content of the selected waste and taking into account the final goal to contribute to biomethane production, a conceptual design of an integrated process based on anaerobic digestion and hydrothermal treatment was provided. In particular, solid streams are directed to an anaerobic digestor, whereas sludge streams are treated with the solid digestate fraction in a hydrothermal carbonization (HTC) reactor, increasing the material recovery of the entire process by producing hydrochar. It is worth mentioning that the sludge streams are not directed with solid streams to the digestor because they could have already been processed in an anaerobic digestion system potentially located within the perimeter of the manufacturer (i.e., food and beverage industrial producer); therefore it was assumed that these waste streams could not provide a significant beneficial effect to the final biomethane production process. Hence, HTC was considered to provide an adequate valorization treatment to these high-moisture sludge streams [18]. In addition, the integration of the two processes through the recirculation of the outlet HTC process water to the digestor was proposed, reaching an adequate inlet moisture content of the anaerobic digestion inlet flow rate higher than 87%w [19].

A preliminary assessment of the proposed waste-to-value process is presented in Section 4.2. This evaluation is based on assumptions from

Table 2. The assumptions adopted for the preliminary design of the integrated process for biomethane and hydrochar production, broken down for the three main sections (i.e., AD, upgrading, HTC).

Anaerobic Digestion (AD) Unit
%VS—Volatile solid mass percentage	11%w
Specific biogas production from AD (i.e., kg of biogas per kg of AD inlet)	0.043 kg/kg
Inlet AD moisture	>87%w
Overall pump efficiency	73%
Biogas upgrading unit
Specific electric consumption with reference to biogas production	0.3 kWh/Nm3
HTC unit and hydrochar combustion unit
Specific electric consumption with reference to total inlet waste in the process	11 kWhel/twaste

and on additional assumptions for the HTC unit following the approach from Bataglia and coworkers [9]. As the anaerobic digestion (AD) unit envisages a recirculation to guarantee the correct moisture fraction within the reactor, the stream in the AD inlet is considered to be roughly 1.6 times greater with respect to the solid stream sent to digestion. Further analysis and a more detailed estimation of process performance are still required and will be addressed by the authors in future studies.

Based on the aforementioned assumptions, mass and energy balance were closed in order to represent specific figures of merit such as (i) BMP—biomethane potential in Nm³/kg of volatile solid (kg_VS); (ii) Y_hydrochar—net hydrochar yield calculated as the mass flow rate of hydrochar sent to storage per tonne of total inlet waste fed to the process; (iii) Wel—specific electric consumption of the plant calculated in terms of kWh_el/t of total inlet waste.

3. Food Waste Screening: The Emilia-Romagna Region Case Study

3.1. Food and Beverage Industry: Number of Enterprises Operating in Emilia-Romagna

Figure 2 and the related breakdown in

Table A1. Food industry enterprise distribution among all provinces in Emilia-Romagna region divided based on NACE 10 groups. Data from ISTAT [20] (Dataset size: 4377 elements). The highest value for each group has been highlighted in bold.

Province	NACE 10	NACE 10 Groups
		10.1	10.2	10.3	10.4	10.5	10.6	10.7	10.8	10.9
Bologna	616	29	2	16	3	25	11	420	104	6
Ferrara	304	17	3	13	0	1	9	231	25	5
Forlì Cesena	393	25	3	9	7	9	17	263	47	13
Modena	776	133	1	14	5	61	14	391	143	14
Parma	872	355	5	19	6	219	17	177	61	13
Piacenza	243	32	1	11	2	24	10	126	31	6
Ravenna	361	14	0	16	3	4	11	258	49	6
Reggio Emilia	530	50	0	8	3	97	14	269	65	24
Rimini	282	13	2	7	14	4	12	165	63	2
Total	4377	668	17	113	43	444	115	2300	588	89

in Appendix A report the number of enterprises per province operating under NACE 10 taken from ISTAT, with Parma ranking the highest, followed by Modena, Bologna, and Reggio Emilia. NACE 10.7, dedicated to the manufacture of bakery and farinaceous products, shows the highest number of enterprises, followed by category 10.1 which includes companies involved in the processing and preserving of meat and production of meat products.

The same analytical approach was used to assess NACE 11: the results reported in Figure 3 based on data from

Table A2. Beverage industry enterprise distribution among all provinces in Emilia-Romagna divided based on NACE 11 groups. Data from ISTAT [20] (Dataset size: 165 elements). The highest value for each group has been highlighted in bold.

Province	NACE 11	NACE 11 Groups
		11.01	11.02	11.03	11.04	11.05	11.06	11.07
Bologna	29	3	16	0	0	9	0	1
Ferrara	8	2	3	0	0	3	0	0
Forlì Cesena	9	1	5	0	0	3	0	0
Modena	29	12	12	0	1	3	0	1
Parma	15	4	5	0	1	5	0	0
Piacenza	16	1	13	0	0	2	0	0
Ravenna	24	4	18	0	0	2	0	0
Reggio Emilia	26	2	17	0	0	4	0	3
Rimini	9	5	0	0	0	2	0	2
Total	165	34	89	0	2	33	0	7

in Appendix A show the highest number of enterprises located in the provinces of Modena, Reggio Emilia, and Bologna. The production of liqueurs and distilled spirits, wine production, and beer production (respectively, NACE 11.01, 11.02, and 11.05) constitute the sectors with the highest number of companies.

3.2. Food and Beverage Waste Production in Emilia-Romagna

Data from ISPRA [14] were analyzed and are reported in

Table 3. National food and beverage and total industrial waste production per Italian region in 2019. Data from ISPRA [14].

Region	Waste Production in Food and Beverage Industries (t/y)	Total Industrial Waste Production (t/y)	Regional % of Food and Beverage Industrial Waste in Terms of Total Regional Industrial Waste	Regional % of Industrial Waste Production for Food and Beverage Industry over National Industrial Food and Beverage Waste
Abruzzo	120,290	2,934,286	4.10%	3.57%
Basilicata	31,523	2,314,039	1.36%	0.94%
Calabria	58,650	2,212,084	2.65%	1.74%
Campania	268,370	8,436,752	3.18%	7.98%
Emilia-Romagna	450,739	13,832,669	3.26%	13.39%
Friuli Venezia Giulia	58,372	4,218,735	1.38%	1.73%
Lazio	150,106	10,164,452	1.48%	4.46%
Liguria	65,361	2,834,408	2.31%	1.94%
Lombardia	583,028	33,540,168	1.74%	17.33%
Marche	82,223	3,743,696	2.20%	2.44%
Molise	1783	601,719	0.30%	0.05%
Piemonte	303,313	11,896,872	2.55%	9.01%
Puglia	204,122	11,388,162	1.79%	6.07%
Sardegna	68,707	3,070,948	2.24%	2.04%
Sicilia	182,281	7,373,307	2.47%	5.42%
Toscana	169,661	10,086,823	1.68%	5.04%
Trentino Alto Adige	89,331	4,686,283	1.91%	2.65%
Umbria	61,553	3,001,267	2.05%	1.83%
Valle d’Aosta	7444	292,639	2.54%	0.22%
Veneto	408,277	17,345,015	2.35%	12.13%
Total	3,365,134	153,974,324	2.19%	100.00%

, showing a comparative analysis of waste production from the food and beverage industry against the total industrial waste production at the national level. This analysis underscores the impact of the food and beverage sector on overall industrial waste production, emphasizing the significant role of the Emilia-Romagna region, which accounts for 3.26% of the total industrial waste production (with Abruzzo ranking first at 4.10%) and 13.39% of the total national food and beverage waste, second only to Lombardy, contributing a share of 17.33%. A graphical representation of these results is shown in Figure 4.

Figure 5 shows the weight of industrial food and beverage waste production at the regional over national level versus the fraction of the same waste over the total industrial waste per region. Based on the plot, the positioning of Emilia-Romagna which is characterized by the relevant weight of the industrial food and beverage waste with respect to the total regional industrial waste, as well as the significant impact of the sector with respect to the total food and beverage waste production. Standing out is the significant amount of food and beverage waste generated in Emilia-Romagna, both regionally and nationally, with reference to NACE sectors 10 and 11.

Table A3. Food industry waste production in 2019 for each of the Emilia-Romagna provinces divided based on NACE 10 groups. Data from ARPAE [15] (Dataset size: 152 elements). The highest value for each group has been highlighted in bold.

Province	Waste Production NACE 10 [t/y]	NACE 10 Groups [t/y]
		10.1	10.2	10.3	10.4	10.5	10.6	10.7	10.8	10.9
Bologna	20,402	984	-	11,981	-	5396	1	243	1798	-
Forlì Cesena	34,793	25,561	-	3839	154	33	25	110	4183	880
Ferrara	18,067	797	-	16,556	-	-	69	600	-	45
Modena	32,590	17,347	-	-	35	2773	99	1319	8331	2686
Piacenza	16,800	548	-	11,796	-	4046	227	-	177	6
Parma	100,926	23,134	109	37,946	20,910	6141	1694	2622	7955	414
Ravenna	68,076	12,237	-	7598	46,213	-	8	1873	83	65
Reggio Emilia	8903	450	68	-	639	5334	8	1126	233	1045
Rimini	1578	104	5	455	-	-	-	32	982	-
Total	302,128	81,162	182	90,172	67,952	23,723	2130	7925	23,742	5141

in Appendix A, together with Figure 6 and

Table A4. Beverage industry enterprise waste production in 2019 for each of the Emilia-Romagna provinces divided based on NACE 11 groups. Data from ARPAE [15] (Dataset size: 33 elements). The highest value for each group has been highlighted in bold.

Province	Waste Production NACE 11 [t/y]	NACE 11 Groups [t/y]
		11.01	11.02	11.03	11.04	11.05	11.06	11.07
Bologna	3098	13	3085	0	0	0	0	0
Forlì Cesena	4200	0	4200	0	0	0	0	0
Ferrara	65	65	0	0	0	0	0	0
Modena	2711	537	2173	0	0	0	0	0
Piacenza	0	0	0	0	0	0	0	0
Parma	1211	50	8	0	0	111	0	1042
Ravenna	563	441	122	0	0	0	0	0
Reggio Emilia	2421	0	2421	0	0	0	0	0
Rimini	15	0	0	0	0	0	0	15
Total	14,284	1107	12,009	0	0	111	0	1057

in Appendix A with Figure 7, respectively, report a breakdown of the NACE 10 and NACE 11 waste production broken down by subcategories. With respect to NACE 10, the meat processing industry (10.1), fruit and vegetable processing (10.3), and the manufacture of vegetable and animal oils and fats (10.4) stand out as the main sub-sectors with peaks of waste production from the provinces of Parma and Ravenna.

With respect to the food industry accounting for more than 300 kt of waste per year for NACE 10 (reference to 2019), the waste production from the beverage industry reported by NACE 11 is significantly lower (~14 kt/y₂₀₁₉). Moreover, in the Forlì-Cesena province, more than 4 kt of beverage waste is recorded, making it the leading province in the region.

With reference to the roughly 450 kt/y of food and beverage industrial waste produced in the Emilia-Romagna region (see Table 3, reference year 2019), the amount reported in Figure 6 and Figure 7 accounts for a total of ~316 kt/y (NACE 10 and 11); as explained in Section 2.1, this value results from the selection of streams labeled within EWC chapter 02, strictly referring to waste from food and beverage processing (i.e., waste from agriculture, horticulture, aquaculture, forestry, hunting and fishing, food preparation, and processing).

3.3. Food and Beverage Industry Characterization by Value Added

A summary of the value added for NACE 10 and 11 is represented in Figure 8 (related data reported in

Table A5. Value added of food and beverage industry sectors for year 2017 in Emilia-Romagna [11].

NACE Code		Value Added [k€]
10.	manufacture of food products.	3,903,329
10.1.	processing and preserving of meat and production of meat products.	1,089,942
10.2.	processing and preserving of fish, crustaceans, and mollusks.	16,945
10.3.	processing and preserving of fruit and vegetables.	452,546
10.4.	manufacture of vegetable and animal oils and fats.	100,393
10.5.	manufacture of dairy products.	541,288
10.6.	manufacture of grain mill products, starches, and starch products.	161,263
10.7.	manufacture of bakery and farinaceous products.	683,122
10.8.	manufacture of other food products.	676,857
10.9.	manufacture of prepared animal feeds.	180,972
11.	manufacture of beverages.	209,551

in Appendix A). This figure highlights the significant contribution of NACE 10.1—the processing and preserving of meat, accounting for over EUR 1 billion in 2017. The manufacture of bakery and other food products, including sugar, cocoa, spices, and more, closely follows, with a value added approaching EUR 700 million. Dairy products and fruit and vegetable manufacturing also contribute significantly, with a value added of around EUR 500 million. In comparison, other sectors show notably lower value added.

3.4. Regional Scenario Based on Selected Figures

A comparative analysis of the selected indicators is reported in Figure 8: despite accounting for a limited number of companies, the value added of NACE group 10.1 is in the order of 1 G€ in 2017, ranking as the highest in Emilia-Romagna. NACE groups 10.3 and 10.4 are characterized by a low number of enterprises and value added around 0.55 G€; however their cumulative contribution is in the order of 50% of the total waste production within the food industry.

Although the meat industry (10.1) demonstrates a relatively higher value added compared to the fruit and vegetable (10.3) and oil and fat (10.4) industries, its waste production needs attention in order to properly manage significant waste streams.

NACE group 10.7 stands out for having the highest number of enterprises among all groups; however, its contribution to food waste production is less than 3% in the region.

Considering their value added, NACE groups 10.3 and 10.4 are among the lowest in the ranking, highlighting the importance of improving waste management in these sectors.

Figure 9 reports the specific waste production per unit of value added. The data shows relevant values of this indicator for NACE groups 10.3 and 10.4, which are therefore characterized by a significant specific production of organic waste affecting the value chain.

4. Results and Discussion

4.1. Selection of Industrial Food Waste Streams of Interest

Based on the considerations from Section 3.4, a more detailed analysis of NACE 10.1, 10.3, and 10.4 was carried out and is reported in Appendix A (see

Table A6. NACE codes and classes, EWC, and waste streams per province. Breakdown sections for each group have been highlighted in bold. Source [15].

NACE Code and Relative Classes
10.1—Processing and preserving of meat and production of meat products       10.11.00. Processing and preserving of meat (excluding poultry meat);       10.12.00. Processing and preserving of poultry meat;       10.13.00. Production of meat and poultry meat products.
10.3—Processing and preserving of fruit and vegetables       10.31.00. Processing and preserving of potatoes;       10.32.00. Manufacture of fruit and vegetable juice;       10.39.00. Other processing and preserving of fruit and vegetables.
10.4—Manufacture of vegetable and animal oils and fats       10.41.00. Production of oils and fats;       10.41.10. Production of olive oil from predominantly non-self-produced olives;       10.41.20. Production of refined or crude oil from oilseeds or oil fruits, primarily not self-produced;       10.41.30. Production of crude or refined animal oils and fats;       10.42.00. Manufacture of margarine and similar edible fats.
NACE Code	EWC—Description	Total (t/y)	Provinces
			BO	FC	MO	PC	PR	RA	RE	RN	FE
10.11.00	020201—sludges from washing and cleaning	8853	105	8433	130	0	17	0	63	104	0
	020203—materials unsuitable for consumption or processing	412	0	0	0	0	411	0	0	0	0
	Total for 10.11.00	9265	105	8433	130	0	428	0	63	104	0
10.13.00	020201—sludges from washing and cleaning	2812	145	0	1468	45	1095	28	31	0	0
	020202—animal-tissue waste	107	0	0	0	0	107	0	0	0	0
	020203—materials unsuitable for consumption or processing	994	0	0	33	0	960	0	0	0	0
	Total for 10.13.00	3913	145	0	1501	45	2163	28	31	0	0
10.3X.00	020304—materials unsuitable for consumption or processing	1721	0	0	0	6	1150	68	0	0	497
10.31.00	020304—materials unsuitable for consumption or processing	4286	4286	0	0	0	0	0	0	0	0
10.32.00	020301—sludges from washing, cleaning, peeling, centrifuging and separation	49	0	0	0	0	0	49	0	0	0
	020304—materials unsuitable for consumption or processing	3741	23	0	0	0	457	3261	0	0	0
	Total for 10.32.00	3790	23	0	0	0	457	3310	0	0	0
10.39.00	020301—sludges from washing, cleaning, peeling, centrifuging and separation	1018	946	26	0	0	45	0	0	0	0
	020304—materials unsuitable for consumption or processing	12,231	624	159	0	545	10,184	189	0	455	76
	Total for 10.39.00	13,249	1570	185	0	545	10,229	189	0	455	76
10.41.10	020301—sludges from washing, cleaning, peeling, centrifuging and separation	485	0	43	0	0	441	0	0	0	0
	020304—materials unsuitable for consumption or processing	4	0	0	0	0	4	0	0	0	0
	Total for 10.41.10	489	0	43	0	0	446	0	0	0	0
10.41.20	020304—materials unsuitable for consumption or processing	36,132	0	0	0	0	0	36,132	0	0	0
10.41.30	020201—sludges from washing and cleaning	9677	0	0	0	0	9502	0	175	0	0
	020203—materials unsuitable for consumption or processing	10,747	0	0	0	0	10,747	0	0	0	0
	Total for 10.41.30	20,424					20,249		175
10.42.00	020304—materials unsuitable for consumption or processing	215	0	0	0	0	215	0	0	0	0

) with a perspective on the geographical food waste distribution in the region.

A summary of relevant streams based on the selected EWC is reported in

Table 4. Annual food waste production for NACE 10.1, 10.3, and 10.4 for four streams FVSW, FVS, SHSW, and SHS. ARPAE [15]. In bold, the total amount of waste selected for the study in t/y₂₀₁₉.

Stream ID	EWC Code and Description	NACE Code	Amount [t]	Total Amount [t]
FVSW Fruit and Vegetable Solid Waste	020304—materials unsuitable for consumption or processing	10.3X.00	1721	58,332
		10.31.00	4286
		10.32.00	3741
		10.39.00	12,231
		10.41.10	4
		10.41.20	36,132
		10.42.00	215
FVS Fruit and Vegetable Sludges	020301—sludges from washing, cleaning, peeling, centrifuging and separation	10.32.00	49	1552
		10.39.00	1018
		10.41.10	485
SHSW Slaughterhouse Solid Waste	020202—animal tissue 020203—materials unsuitable for consumption or processing	10.11.00	412	12,260
		10.13.00	1101
		10.41.30	10,747
SHS Slaughterhouse Sludges	020201—sludges from washing and cleaning	10.11.00	8853	21,342
		10.13.00	2812
		10.41.30	9677
Total (sludges + solid waste)				93,486

: food waste streams were grouped into two main categories, solid waste and sludges, with a total amount per year equal to more than 93 kt. The annual flow rate can be assumed for the design of suitable valorization pathways (see Section 4.2).

A literature review was conducted on food waste streams to identify a range of compositions expressed in terms of solid fraction (broken down into ashes, lipids, proteins, and carbohydrates) and moisture. The results reported in

Table 5. Literature analysis on waste composition (weight base) for the four selected streams in bold.

FVSW Composition	Moisture	Ashes	Lipids	Proteins	Carbohydrates
Edwiges et al. [21]	90.5%	0.8%	0.4%	1.4%	7.0%
Miramontes-Martínez et al. [22]	89.1%	0.8%	0.6%	0.7%	8.8%
Zhao et al. [23]	52.2%	0.2%	0.9%	7.7%	39.1%
FVS composition	Moisture	Ashes	Lipids	Proteins	Carbohydrates
Nielfa et al. [24]	92.8%	1.5%	0.2%	3.3%	2.2%
SHSW composition	Moisture	Ashes	Lipids	Proteins	Carbohydrates
Miramontes-Martínez et al. [22]	88.2%	0.6%	4.6%	5.5%	1.1%
Hejnfelt et al. [25]	73.1%	3.7%	5.5%	17.2%	0.6%
Handous et al. [26]	74.5%	5.0%	5.6%	14.5%	0.4%
Palatsi et al. [27]	47.3%	0.6%	43.2%	6.5%	2.4%
Palatsi et al. [27]	62.5%	0.8%	24.9%	7.0%	4.8%
Cuetos et al. [28]	71.7%	2.3%	10.5%	10.1%	5.4%
SHS composition	Moisture	Ashes	Lipids	Proteins	Carbohydrates
Handous et al. [26]	91.9%	1.1%	0.0%	6.9%	0.1%
Palatsi et al. [27]	75.8%	0.9%	10.7%	6.8%	5.8%
Palatsi et al. [27]	90.4%	1.3%	5.0%	3.1%	0.1%
Bayr [29]	97.8%	0.2%	1.6%	0.2%	0.2%
Bayr [29]	99.0%	0.1%	0.1%	0.8%	0.0%

show the high moisture content for all the selected streams; meanwhile, lipids and proteins attain significant fractions in SHSW.

For slaughterhouse waste, the composition from Hejnfelt et al. [25] refers to data concerning untreated mixed pork waste from the European area. Regarding SHSW streams, data from Palatsi et al. [27] are quite different when compared to the other sources, while Miramontes-Martínez et al. [22] and Handous et al. [26] refer to waste streams coming, respectively, from New Mexico and Tunisia. Data from Hejnfelt et al. [25] and Cuetos et al. [28] refer to studies performed in Denmark and Spain.

For the SHS stream, ref. [26] refers to non-European areas. The remaining two sources refer to studies on streams coming, respectively, from Spain [27] and Finland [29].

For fruit and vegetable waste streams, no literature sources referring to the European zone have been found. For FVS, only one source was identified [24]. The analysis of FVSW reports on the work from Zhao et al. [23] with a composition quite different from the one recorded in Edwiges et al. [21] and Miramontes-Martínez et al. [22].

Paving the way for the design of alternative valorization strategies for the selected streams, an analysis of current waste management pathways is reported in Figure 10, showing how the different wastes, classified by the respective EWC code, were processed in 2019. The distribution of waste management options shown in Figure 10 was derived from official data provided by ARPAE [15].

For each selected EWC code (020201, 020203, 020301, 020304), ARPAE reports the amounts annually directed to the different management operations (R1, R2–R12, R13, D1, D2–D14, D15) according to Directive 2008/98/EC. The percentages shown in the figure correspond to the share of each operation with respect to the total amount of waste recorded under that EWC code in Emilia-Romagna in 2019. For example, the 69% of EWC 020201 (slaughterhouse sludges) reported as material recovery (R2-R12) corresponds to the fraction officially recorded by ARPAE as sent to composting or anaerobic digestion.

As highlighted in Figure 10, sludge streams (EWC 020201 included in SHS and EWC 020301 from FVS) are sent to disposal operations or to material recovery processes, among which composting and anaerobic digestion are included.

Solid waste from slaughterhouses (EWC 020203—SHSW) are mainly directed to energy recovery processes and solid waste from food and vegetable processing (EWC 020304—FVSW) to energy and material recovery processes. It is worth noting that currently, direct disposal (D1) is almost a negligible option for all these waste streams.

Within this perspective, the alternative food waste process described in Section 4.2 results in the production of biomethane and hydrochar; therefore, it may be considered a high-value-recovery operation with reference to the waste hierarchy (Directive 2008/98/EC); thus, it may be considered a proper alternative to disposal operations but also to energy recovery operations, due to the high waste moisture content. Indeed, this novel process can offer an interesting option for the conventional AD process thanks to the possible beneficial effects from the integration with HTC and a higher-level recovery solution compared to composting thanks to the generation of biomethane and hydrochar.

4.2. Conceptual Design of Integrated Waste-to-Value Process

The proposed process combines anaerobic digestion (AD) and hydrothermal carbonization to enhance biogas production. The produced hydrochar is partially burnt to satisfy the HTC thermal demand. The wet AD process features solid food waste and water recycled from HTC, with a total solid content of about 12% and an AD temperature of 55 °C. After filtration to control water content, the solid-rich stream is mixed with food industry sludges and pressurized up to roughly 35 bar before entering the HTC unit. Food sludges are assumed to be treated into previous digestion units at source; therefore secondary treatment is only performed in HTC.

In HTC, pre-heating at 150 °C is carried out with circulating water; the mixture is then heated up to 210 °C with diathermic oil from a furnace fed with hydrochar from the HTC process. The cooling section of the HTC unit is operated with water with pressurized water (25 bar) used for the aforementioned pre-heating stage. The mixture is finally cooled with cooling water down to 35 °C. After separation and filtration by means of a filter press, a liquid fraction and the solid hydrochar are recovered. The liquid is returned to the digester, while part of the hydrochar is used in the furnace to support HTC energy demand. The gaseous output from HTC has to be processed through adequate treatment strategies which may involve acid/alkaline baths or adsorption, depending on the stream composition.

The process requires a biogas upgrading unit, where biogas from the digester is directed by a fan. Biogas is cooled to 25 °C to remove water, while an activated carbon bed removes H₂S. The gas stream mainly composed of biomethane and CO₂ is compressed to 15 bar and purified to over 98% CH₄ through membrane separation. The resulting biomethane is then pressurized, achieving 70 bar to meet national gas grid standards.

A preliminary evaluation of the process performance is reported in

Table 6. Preliminary mass and energy balance of integrated process for biomethane and hydrochar production from selected food waste streams. The main streams and indicators are reported in the two sections bold highlighted in bold.

Stream	Description	Value	Unit
1	FVSW	58,332	t/y
2	SHSW	12,260	t/y
5	FVS	1552	t/y
6	SHS	21,342	t/y
waste	Total inlet waste (stream n.1 + 2 + 5 + 6)	93,486	t/y
Indicator	Description	Value	Unit
BMP	Biomethane potential	0.233	Nm3/kgVS(ADin)
Yhydrochar	Net hydrochar yield (i.e., hydrochar to storage)	130	kghydrochar/twaste
Wel	Specific electric consumption	33	kWhel/twaste

where indicators of mass and energy balance are included. The evaluation provides the first quantitative estimation of the material recovery and electric specific energy consumption of the process, based on the assumptions reported in Section 2.2. The analysis shows a biomethane potential in the order of 0.2 Nm³/kg_VS (volatile solid—VS), with an overall electric consumption of 33 kWh_el/t of input waste broken down as from Figure 11. The electric demand is mainly due to the upgrading unit needed to separate biomethane for network injection (pressure in the order of 70 bar).

A dedicated process flow diagram is shown in Figure 12, highlighting the main process sections, material recirculation, and energy integration strategies. Future work will be based on process simulation activities and the definition of a techno-economic assessment [30,31] for a more accurate evaluation of the process performance, comparing the alternative approach to benchmark technologies such as conventional energy recovery from waste.

5. Conclusions

Emilia-Romagna accounts for 13.39% of Italy’s total food and beverage industrial waste, second only to Lombardy, and contributes 3.26% to the total industrial waste production at the national level.

This study provides a perspective on Emilia-Romagna’s food and beverage waste production focusing on selected streams with residual organic content (plastic streams or metal fractions, hazardous waste, or waste from chemical treatments and other streams are not included in the analysis), which may be suitable for novel valorization routes. The screening is based on selected indicators such as the number of companies, their value added, and the recorded waste production from NACE 10 and 11.

Detailed sectoral analysis reveals that the meat processing industry (NACE 10.1) is the largest contributor in terms of economic value, with over EUR 1 billion in value added recorded in 2017. Other relevant contributors include fruit and vegetable processing (NACE 10.3) and the manufacture of vegetable and animal oils and fats (NACE 10.4), which collectively cover almost 50% of the region’s selected industrial food and beverage waste streams. NACE 10.1, 10.3, and 10.4 account for more than 75% of the regional industrial food and beverage waste produced with respect to the reference year 2019. Moreover, the analysis of the specific waste generation per unit of value added underscores the interest in sectors 10.3 and 10.4, which may benefit advanced waste management strategies.

Therefore, the industrial food waste produced by the identified sectors (i.e., NACE 10.1, 10.3, and 10.4) was further characterized based on its EWC and sorted into two main groups—solid waste and sludges—amounting to over 93 kt per year, suitable for further recovery processes. Assuming a constant availability of the selected fluxes on annual basis, this provides the first specification for the design of a novel valorization pathway aiming at supporting biomethane production in Italy. Hence, a conceptual integrated waste-to-value process combining anaerobic digestion and hydrothermal carbonization is proposed to optimize biogas production while maximizing carbon recovery through hydrochar production. This approach offers a new option for the identified waste streams within a circular economy perspective.

Further investigation is necessary, focusing on process simulation and the definition of a techno-economic assessment in order to properly characterize the here-defined alternative valorization process, estimating yields and energy performance.