Spatial Differentiation of Agricultural Biomass Potential in Polish Voivodeships

Abstract

The main aim of the article is to assess the potential of agricultural biomass and the possibility of its use for energy purposes in Polish voivodeships. Five sources of agricultural biomass were analyzed: straw, hay, waste wood from orchards, perennial energy crops, and natural fertilizers. For the purposes of the research, the theoretical and technical potential of agricultural biomass was estimated. The potential of agricultural biomass was estimated for Polish voivodeships based on the data of the 2020 Agricultural Census. The conducted research shows that Polish voivodeships have a significant theoretical potential for agricultural biomass. However, due to the fact that biomass is widely used in plant production (as a natural fertilizer) and animal production (as fodder or bedding), only about 40% of the identified theoretical potential can be used for energy purposes. The research also shows that the dominant source of agricultural biomass that can be used in Poland is straw from cereal crops. Moreover, a significant part of the identified potential is located in the western part of Poland (Wielkopolskie, Dolnośląskie, Kujawsko-Pomorskie, Zachodniopomorskie voivodships) and partly in the east (Lubelskie voivodship). Although the possibility of using natural fertilizers for energy purposes has not been identified, the theoretical potential of which is very high, an increase in the importance of renewable energy from agricultural biogas plants should be expected in the near future. This is due to the changes taking place in the storage and management of natural fertilizers.

1. Introduction

Access to food is one of the fundamental human needs. Therefore, both individual households and national economies should ensure an adequate amount of food supply [1]. Adequate food supply is satisfied with agricultural production, which in subsequent stages is processed by food industry enterprises [2]. Agriculture, performing the basic economic function in rural areas, determines the direction of their socio-economic development, provides jobs for rural residents, and shapes the spatial structure of rural areas. In addition, in places where traditional methods of production and land development are preserved, the cultural landscape of the village is also shaped by offering original rural layouts and historic buildings [3]. Thus, agriculture, being an essential production process, makes a significant contribution to both society and the economy and is also a fundamental driving force in rural areas [4,5,6,7]. For these reasons, agriculture is and will be an important element of both the economic activity of individual countries as well as agricultural, social, and environmental policy [2]. Although, as emphasized by Loizou et al. [8], agriculture is usually not treated as the main sector of the economy in developed countries, and its role as a factor of economic growth is underestimated. Therefore, the development of agriculture is necessary for the economic development of the state, regardless of its level of development. This is due to the fact that agriculture is of great importance in the overall economic development through its product input (provision of food and raw materials), contribution to the market (providing a market for the production and consumption of goods produced in the non-agricultural sector), factor contribution (making labor and capital available to the non-agricultural sector), and foreign exchange contribution [6]. In addition, agriculture plays a significant role in reducing rural poverty [9], as well as in ensuring food security [10]. Ensuring food self-sufficiency is particularly important during the disruption of international trade in agricultural products and food [10].

Agriculture in Poland is an important sector of the economy, which is indicated primarily by land use and the employment structure of the population [3]. In recent years, in Poland, agricultural land constitutes about 60% of the country’s area [11]. The number of people employed in agriculture has also remained at a similar, quite high level for a long time, constituting about 14% of all working people. Such high employment in agriculture is mainly due to the fragmented agrarian structure. The importance of this sector in Poland is also indicated by its share in GDP—in recent years, it has fluctuated at the level of 2.4–2.6%. Similar conclusions can be drawn from the share of agriculture in the production of the global national economy, which in recent years has been in the range of 3.0–3.2% [12]. Thanks to the great importance of agriculture, Poland has for years been one of the countries with high self-sufficiency in the production of most basic agricultural raw materials for consumption and food production, with a surplus allowing for sale on markets outside the country [10]. The special role of agriculture in the social and economic development of rural areas should also be emphasized. In addition, due to the fact that agriculture takes place on more than half of the total area of the country, it determines the main functions and directions of land use, as well as shapes the natural environment and landscape. The purity of water, air, and soil, as well as the diversity of plant and animal species, depend to a large extent on agricultural management [3].

The growing population has resulted in a significant increase in demand for agricultural products. Such high demand requires changes in the traditional model of agriculture. Therefore, modernization and specialization of agricultural production are currently observed in Poland. Modern agriculture produces food raw materials using industrial methods, thanks to which much greater economic benefits are achieved than in the case of production using traditional methods [3]. However, in recent years, as a result of the aforementioned processes of intensification and concentration of production, agriculture in Poland has increased its role as an emitter of greenhouse gases and other types of pollutants (e.g., ammonia). The reason for the increased emissions is mainly the consumption of production means (fertilizers, pesticides, fuels, energy), the management of natural fertilizers, agricultural practices, and the burning of post-harvest residues. In addition, the increase in emissions is also due to changes in the stock of the main livestock species, such as cattle or pigs [10].

According to the report of the National Center for Balancing and Management of Emissions (KOBiZE), in 2020, the total emissions of greenhouse gases of agricultural origin amounted to 9.1% of the total emissions of the state. Agriculture in Poland is the main source of nitrous oxide (N₂O) emissions, accounting for 81.8% of total nitrous oxide emissions; 68.9% of these emissions come from land use (nitrogen fertilization) and 12.9% from livestock manure management. Methane (CH₄) emissions from agriculture in 2020 accounted for 31.9% of emissions from all domestic sources. The main sources of methane emissions in Polish agriculture are enteric fermentation (91.3%) and manure management (8.5%). CO₂ emissions in Polish agriculture are marginal and amount to only 0.5% [13]. For this reason, the new assumptions of the agricultural policy of the European Union assume the development of so-called sustainable agriculture, which is focused on the use of land resources that do not destroy their natural sources but allow meeting the basic needs of subsequent generations of producers and consumers [3]. In Europe, sustainable agricultural production is regulated by the provisions on cross-compliance requirements in the field of environmental protection, which are set out in the Common Agricultural Policy (CAP) [14]. The Polish Strategic Plan for the Common Agricultural Policy 2023–2027 indicates that agriculture is one of the important sectors of the economy, where opportunities for a positive impact on the climate and the natural environment should be sought in greater production and use of energy from renewable sources (RES). The post-2020 EU climate and energy policy is moving towards further increasing energy efficiency. This means that increasing energy efficiency will also have to be sought in agriculture [15].

With the economic development of countries and the development of agriculture, modern society faces two very difficult challenges. First, it is necessary to increase biomass production to meet future demand for food, materials, and bioenergy. Second, the negative impacts of current (and future) land use need to be addressed [16,17]. Due to the emerging problems related to the depletion of conventional fuel resources, as well as the growing concern for the natural environment, environmentally friendly solutions are currently being sought in agriculture. A solution that may reduce the negative impact of agriculture on the environment may be the use of biomass produced in the production process. Biomass used for energy purposes can contribute to reducing the negative environmental effects that are currently visible in agricultural production (plant and animal) due to its benefits. Among the main benefits of biomass, it should be emphasized that it is a universal source, as it can be used to produce heat and electricity, as well as fuel for transport. In addition, by using biomass for energy purposes, the amount of waste and residues resulting from agricultural activities can be reduced. In addition, it is also possible to reduce the emission intensity of agriculture, e.g., by processing natural fertilizers or using biofuels. Finally, the use of biomass can bring benefits to the inhabitants of the area where it occurs by improving energy security–energy production, creating new jobs, and increasing the income opportunities for farmers by selling biomass for energy purposes [18,19]. In Europe, a significant amount of biomass comes from crop residues, forestry waste, processing waste, and recovered wood [14]. Huge amounts of agricultural biomass are produced all over the world, which can be converted into environmentally friendly energy using various procedures [20]. Many types of biomass produced in agriculture can be converted into energy, also reducing their emissivity, i.e., natural fertilizers and post-harvest residues. In addition, agricultural space can be better used by allocating low-quality, wasteland, or contaminated land for the cultivation of perennial crops. It should also be emphasized that biomass is not only a renewable source but also a local one that contributes to building energy independence [21]. In addition, it is also worth emphasizing that surplus or residual biomass is not specifically produced for use in the energy sector but results from economic activity that would take place anyway. If such a system is maintained, the use of biomass for the production of renewable energy may increase without a negative impact on the environment [22]. In addition, a large share of agricultural land in the total area of Poland, together with the identification of production in Polish agriculture, should allow for the allocation of part of agricultural land for energy crops [23].

The literature on the subject provides a lot of evidence that biomass is of great importance in meeting the challenges that are currently emerging. Sherwood [24] indicates in his research that biomass is of great importance in the circular economy in terms of material products and energy supply. The technical and economic analysis carried out by Saleem [20] indicates the possibility of using agricultural biomass as a competitive source of energy. However, Liu et al. [25], in their research in China, emphasize that the use of biomass from crop residues can contribute to reducing the problem of energy shortage, improve the agricultural system, and reduce fertilizer pollution. Cintas et al. [26] emphasize that bioenergy can contribute to achieving the climate goals set by the European Union, as well as mitigate the effects of current land use. Mandley et al. [27] also indicate that biomass in EU countries may have significant additional potential to implement efforts to reduce greenhouse gas emissions and limit the temperature increase to 2 °C. Gyamfi et al. [28], studying emerging countries, observed that the use of energy from biomass reduces emissions, which indicates the key role of biomass consumption in creating an ecologically friendly environment and environmental sustainability.

In the literature on the subject, in addition to indicating the importance of biomass, one can also find many studies indicating the sources of biomass with the greatest potential for use for energy purposes. According to Knapek et al. [29], the main resources of biomass that can be used for energy purposes are residual biomass (straw from agricultural production), intentionally cultivated biomass of energy crops on agricultural land, unused biomass from permanent grassland (grass, hay), as well as residues from felling trees. This is also confirmed by studies by other authors conducting research in various parts of Europe and the world. Vaish et al. [30], studying the possibilities of alternative use of biomass in agricultural provinces of India, identified a huge energy potential from crop residues, which are usually treated as waste. Liu et al. [25], conducting research in China, also identified very large biomass resources from crop residues that can be used for energy purposes, which are currently thrown away or burned in the fields. Research by Scarlat et al. [31] proves that in EU countries, there is a significant potential for agricultural crop residues that can be used for energy purposes. Cintas et al. [26], who conducted research in EU countries, showed that supporting coal-fired power plants with energy crops cultivated on agricultural land will bring significant climate benefits. In addition, the cultivation of energy crops itself may have a beneficial effect on the content of organic carbon in the soil in most of the analyzed countries. Hamelin et al. [32] showed in their research that the main source of biomass in the European Union that can be used for energy purposes is straw from cereal cultivation. Ericsson and Nilsson [33] drew attention to the great possibilities of using energy crops for energy purposes. Other scientists [34,35,36] studying the potential of agricultural residues in different parts of the world (Sudan, Ghana, Serbia) also noted great possibilities of its use for energy purposes, additionally emphasizing the possibilities of solving the problem of energy shortages in these countries. Moreover, Mahmood et al. [37] indicate that biogas derived from biomass is also a promising renewable energy source, the importance of which is growing both in Europe and in other countries of the world. On the other hand, Bechis [38], in his research, indicates the benefits of using agricultural waste and tree felling for energy purposes in modern stoves, which are characterized by higher efficiency and safety than traditional wood-fired installations.

The use of energy from renewable sources is also an important part of European Union policy. Directive (EU) 2018/2001 of the European Parliament and of the Council of December 11, 2018, emphasized that the use of energy from renewable sources is very important from the point of view of security of energy supply, sustainable energy, and technological development and innovation while ensuring environmental, social, and health benefits. In addition, benefits are also expected in terms of employment opportunities and regional development, especially in rural and isolated areas, in areas with low population density, and in partial deindustrialization [39]. According to this directive, by 2030 in the European Union, 32% of energy is to come from renewable sources. On the other hand, pursuant to Regulation (EU) 2018/199, Member States have planned their national targets [40]. Taking into account the national potential of renewable resources, Poland has declared that by 2030, the share of RES in gross marginal energy consumption will be at the level of 23%, and by 2040 this share is estimated at 28.5%. In Poland, the development of energy from renewable sources has been recognized as one of the specific objectives of the Polish Energy Policy until 2040. According to this document, the share of energy from renewable sources will be higher than declared due to the achievement of technological and economic maturity of individual technologies. Therefore, after 2025, it is expected that the use of RES will systematically increase and will amount to at least 32% net by 2030 and 40% in 2040. As far as biomass is concerned, its multi-directional use is assumed (in transport, heating, and power engineering), thanks to which efforts are made to reduce emissions of the energy system. In terms of transport, it is assumed that biomethane produced from biogas, especially agricultural biogas from waste and by-products from agriculture and food processing, will be used. In addition, in accordance with the energy policy adopted in Poland, it is assumed that biomass has the greatest potential for achieving the RES target in the heating sector, mainly due to the availability of fuel, as well as the technical and economic parameters of the installation. Biomass and biogas are also mentioned as a source of RES in electricity production [41]. As indicated by previous research, biomass is one of the most popular energy sources, having a wide range of applications, both in the production of electricity and heat. Therefore, its importance in the sector of renewable sources is constantly increasing. Its prospective importance in the development of renewable energy is also determined by the fact that compared to solar or wind energy, energy from biomass is one of the more stable sources of renewable energy [42]. The great importance of biomass in Poland is indicated by its share of the total production of energy from renewable sources. According to the latest data from the Central Statistical Office in Poland, the share of renewable energy from biomass in 2020 was 82%, including solid biofuels—71.6%, liquid biofuels—7.8%, and biogas—2.6% [43]. A characteristic feature of renewable energy production in Poland is a large share of solid biomass. However, high dynamics of renewable energy production from agriculture are also observed [15].

However, the future use of this raw material for energy production will depend on its economic availability, which depends on such factors as price formation and availability of imports, development of other coal technologies, viability of non-energy bio-based products, and climate targets. Similar conclusions were reached by Rehfeldt et al. [44], claiming that despite the significant potential for rapid emission reductions by switching to biomass and electricity, deep decarbonization consistent with climate goals requires innovative production processes that are only available in the long term. According to Muscat et al. [45], European Union countries will gradually switch to a bioeconomy to meet emerging requirements (reduction of dependence on non-renewable resources, sustainable management of natural resources, food security), and biomass will become an increasingly important resource. However, this will require careful and sustainable management, mainly because biomass comes from many different economic sectors and is regulated by different policies. Additionally, Wyszyński et al. [23] indicate, in the case of the development of renewable energy from biomass, the need to create optimal conditions for the development of distributed energy based on locally available resources and to introduce a greater, sustainable involvement of agricultural areas for this purpose.

Despite the many advantages of using biomass for energy purposes and evidence of its potential, some risks of its use should be taken into account. Firstly, the amount of available biomass cannot be treated as a constant value due to changes in the availability of agricultural land and the structure of crops. However, in the short term, no changes should be expected due to various aspects related to biodiversity and the environment [46]. Secondly, the use of biomass is effectively justified if it is used at the place of its origin or in the vicinity [38], which makes it necessary to invest in modern technologies. Thirdly, land use change is often viewed negatively in terms of the effects of deforestation and the expansion of plantations. On the other hand, the strategic location of appropriate perennial production systems in the agricultural landscape can reduce the negative environmental impact of crop production while providing biomass for the bioeconomy [16], especially as research shows the goals of the bioeconomy policy and the goals of the agri-food policy are largely considered common [45]. Finally, it should be emphasized that energy is an indicator of the socio-economic development of each country and has become an indispensable part of modern society. However, despite several renewable energy sources, biomass sources are still underutilized due to the lack of a standard national resource estimation policy [30].

Due to the arguments raised above, the main purpose of the article is to assess the potential of agricultural biomass and the possibility of its use for energy purposes in Polish voivodships. For the purposes of the study, three research questions were adopted: How large is the theoretical potential of agricultural biomass in Poland? How can part of the identified theoretical potential of agricultural biomass be used for energy purposes? Which sources of agricultural biomass are of the greatest importance in Poland?

2. Materials and Methods

The conducted analysis concerns the determination of the size of the energy potential of biomass of agricultural origin. Taking into account the possibility of using agriculture as a source of raw materials for the production of renewable energy, such sources are:

• − Straw from the cultivation of cereals;
• − Hay from meadows and pastures;
• − By-products from livestock farming (natural fertilizers);
• − Wood from pruning orchards;
• − Plants intended specifically for energy purposes grown on fallow land (willow).

The first four sources of biomass are most often by-products or residues that are not fully used in agriculture. However, in the case of the last biomass source included in the analysis, i.e., energy crops, it was assumed that land not fully used in agriculture would be used for these purposes. The method of estimating the energy potential of individual sources of agricultural origin is presented in Table 1. The assessment of the potential of biomass of agricultural origin was made on a regional basis. The study includes an estimation of the potential for 16 Polish voivodeships.

In the literature on the subject, there are various ways of presenting the potential of renewable energy sources—theoretical, technical, economic, or available potential. Differences in the presentation of the potential result from the method of estimating the size of raw materials that can be used for energy purposes and the efficiency of devices processing the raw material into usable energy. In the presented study, the theoretical and technical potential was estimated. The theoretical potential is usually considered to be the total amount of biomass that occurs in a given area, taking into account the efficiency of devices converting the raw material into energy. The technical potential usually includes the amount of biomass produced in a given area, decreased by the amount used for purposes other than energy, and the efficiency of devices converting the raw material into energy [47,48]. It should be emphasized that the main function of agriculture is food production, thus ensuring food security. Therefore, only raw materials of agricultural origin that are redundant or surplus should be used for energy purposes [49].

Statistical data from the 2020 Agricultural Census were used to estimate the potential of agricultural biomass. The scope, form, and mode of work related to the conduct of the Agricultural Census, as well as the preparation and processing of its results, are regulated by the Act of 31 July 2019 on the 2020 Agricultural Census [50]. The census was conducted by the Central Statistical Office in Poland in the period from 1 September to 30 November 2020, as of 1 June 2020. Data from the National Agricultural Census allow for accurate analysis related to agriculture. These data are also the basis for making decisions of a strategic nature by the authorities at the central and regional levels [51].

Table 1. The method of estimating the theoretical and technical potential of selected agricultural biomass sources.

The Method of Estimating the Theoretical and Technical Potential of Selected Biomass Sources
Source of Biomass	Theoretical Potential	Technical Potential
straw from cereal crops	$P={\displaystyle \sum _{i=1}^n}\mathrm{A} \times \mathrm{Y} \times { \mathrm{w}}_{\mathrm{zs}}\times 13\times 0\%$ where: P–straw potential, A—cultivation area of a given plant species (ha), Y—actual grain yield of a given plant species (t/ha), wzs—ratio of straw yield to grain yield, 13 GJ/t—energy value of straw; 80%—efficiency of devices processing the raw material into usable energy [52].	$P={\displaystyle \sum _{i=1}^n}\mathrm{N} \times 13\times 80\%$ where: P—potential of straw, N—surplus of straw in a given area, 13 GJ/t—energy value of straw, 80%—efficiency of equipment converting raw material into usable energy [52].
hay from meadows and pastures	${\mathrm{P}}_{\mathrm{ts}}=\mathrm{A}\times \mathrm{Y}\times 13.4 \times$80% where: Pts—hay potential; A—area of permanent grasslands, Y—hay yield from meadows and pastures; 13.4 GJ/t—energy value of hay, 80%—equipment efficiency [53].	Pts = A $\times$ Y $\times$ wws $\times$ 13.4 $\times$ 80% where: Pts—hay potential; A—area of permanent grasslands; Y—hay yield from meadows and pastures; wws—coefficient of use for energy purposes; 13.4 GJ/t—energy value of hay; 80%—device efficiency [53].
plants intended specifically for energy purposes grown on fallow land	${\mathrm{P}}_{\mathrm{re}}={\mathrm{A}}_{\mathrm{gp}}\times {\mathrm{Y}}_{\mathrm{re}} (\mathrm{t}/\mathrm{ha})\times 18 (\mathrm{GJ}/\mathrm{t}) \times$ 80% where: Pre—the potential of perennial plants intended for energy purposes, Agp—the area of land suitable for the cultivation of energy crops (ha), Yre—the average yield of selected energy crops (t/ha/year), 18 GJ/t—energy value of willow, 80%—efficiency of biomass burning devices [21].	Pre = Ad $\times$ Yre (t/ha) $\times$ 18 (GJ/t) $\times$ 80% where: Pre—potential of perennial plants intended for energy purposes, Ad—area of land available for the cultivation of energy crops (ha), Yre—average yield of selected energy crops (t ha/ha/year), 18 GJ/t—energy value of willow, 80%—efficiency of devices for burning biomass [21].
wood from orchard maintenance pruning	Zds = A $\times$ ud $\times$ we $\times$ 80% (GJ/rok) where: Zds—energy potential of waste wood resources from orchards (GJ), A–orchard area (ha), ud–yield of waste wood (in m3) from 1 ha of orchards, we—energy value of wood, 80%—efficiency of devices [54].	Zds = A $\times$ ud $\times$ we $\times$ 80% (GJ/rok) where: Zds—energy potential of waste wood resources from orchards (GJ), A—orchard area (ha), ud—yield of waste wood (in m3) from 1 ha of orchards, we—energy value of wood, 80%—equipment efficiency [54].
by-products from livestock farming	Pbr = L $\times$ Wbsd $\times$ 365 $\times$ zCH4 $\times$ wem $\times$ 80% (MJ/year) where: Pbr—potential of agricultural biogas (m3), L—number of LU, Wbsd—biogas production index per LU (m3 · LU−1·d−1), zCH4—methane content in biogas (vol.%), wem—energy value of m3 of biomethane (MJ), 80%—equipment efficiency [52,55].	Pbr = Nnn $\times$ wem $\times$ 80% (MJ/rok) where: Pbr—agricultural biogas potential (m3), Nnn—surplus of natural fertilizers; wem—energy value of m3 of biomethane (MJ), 80%—equipment efficiency [52,55].

Source: Author’s own elaboration.

Table 1. The method of estimating the theoretical and technical potential of selected agricultural biomass sources.

The Method of Estimating the Theoretical and Technical Potential of Selected Biomass Sources
Source of Biomass	Theoretical Potential	Technical Potential
straw from cereal crops	$P={\displaystyle \sum _{i=1}^n}\mathrm{A} \times \mathrm{Y} \times { \mathrm{w}}_{\mathrm{zs}}\times 13\times 0\%$ where: P–straw potential, A—cultivation area of a given plant species (ha), Y—actual grain yield of a given plant species (t/ha), wzs—ratio of straw yield to grain yield, 13 GJ/t—energy value of straw; 80%—efficiency of devices processing the raw material into usable energy [52].	$P={\displaystyle \sum _{i=1}^n}\mathrm{N} \times 13\times 80\%$ where: P—potential of straw, N—surplus of straw in a given area, 13 GJ/t—energy value of straw, 80%—efficiency of equipment converting raw material into usable energy [52].
hay from meadows and pastures	${\mathrm{P}}_{\mathrm{ts}}=\mathrm{A}\times \mathrm{Y}\times 13.4 \times$80% where: Pts—hay potential; A—area of permanent grasslands, Y—hay yield from meadows and pastures; 13.4 GJ/t—energy value of hay, 80%—equipment efficiency [53].	Pts = A $\times$ Y $\times$ wws $\times$ 13.4 $\times$ 80% where: Pts—hay potential; A—area of permanent grasslands; Y—hay yield from meadows and pastures; wws—coefficient of use for energy purposes; 13.4 GJ/t—energy value of hay; 80%—device efficiency [53].
plants intended specifically for energy purposes grown on fallow land	${\mathrm{P}}_{\mathrm{re}}={\mathrm{A}}_{\mathrm{gp}}\times {\mathrm{Y}}_{\mathrm{re}} (\mathrm{t}/\mathrm{ha})\times 18 (\mathrm{GJ}/\mathrm{t}) \times$ 80% where: Pre—the potential of perennial plants intended for energy purposes, Agp—the area of land suitable for the cultivation of energy crops (ha), Yre—the average yield of selected energy crops (t/ha/year), 18 GJ/t—energy value of willow, 80%—efficiency of biomass burning devices [21].	Pre = Ad $\times$ Yre (t/ha) $\times$ 18 (GJ/t) $\times$ 80% where: Pre—potential of perennial plants intended for energy purposes, Ad—area of land available for the cultivation of energy crops (ha), Yre—average yield of selected energy crops (t ha/ha/year), 18 GJ/t—energy value of willow, 80%—efficiency of devices for burning biomass [21].
wood from orchard maintenance pruning	Zds = A $\times$ ud $\times$ we $\times$ 80% (GJ/rok) where: Zds—energy potential of waste wood resources from orchards (GJ), A–orchard area (ha), ud–yield of waste wood (in m3) from 1 ha of orchards, we—energy value of wood, 80%—efficiency of devices [54].	Zds = A $\times$ ud $\times$ we $\times$ 80% (GJ/rok) where: Zds—energy potential of waste wood resources from orchards (GJ), A—orchard area (ha), ud—yield of waste wood (in m3) from 1 ha of orchards, we—energy value of wood, 80%—equipment efficiency [54].
by-products from livestock farming	Pbr = L $\times$ Wbsd $\times$ 365 $\times$ zCH4 $\times$ wem $\times$ 80% (MJ/year) where: Pbr—potential of agricultural biogas (m3), L—number of LU, Wbsd—biogas production index per LU (m3 · LU−1·d−1), zCH4—methane content in biogas (vol.%), wem—energy value of m3 of biomethane (MJ), 80%—equipment efficiency [52,55].	Pbr = Nnn $\times$ wem $\times$ 80% (MJ/rok) where: Pbr—agricultural biogas potential (m3), Nnn—surplus of natural fertilizers; wem—energy value of m3 of biomethane (MJ), 80%—equipment efficiency [52,55].

Source: Author’s own elaboration.

The theoretical potential of straw was estimated as the product of the cultivation area of a given plant species, grain yield of a given plant species, the ratio of straw yield to grain yield, energy value, and efficiency of devices converting the raw material into usable energy. Data on the cultivation area of a given plant species (wheat, rye, barley, oats, triticale, cereal mixtures, corn for grain, rape, and turnip rape) and their actual yield were obtained from the website of the Central Statistical Office in Poland [11]. On the basis of the collected data, cereal yields were determined. On the basis of cereal yields and the normative ratio of straw yield to grain yield, the amount of straw production was determined for each voivodeship. According to Gradziuk [56], the following standards were adopted for the ratio of straw yield to grain yield for individual cereals: wheat: 0.8; rye: 1.4; barley: 0.9; oats: 1.05; triticale: 0.8; cereal mixes: 0.95; grain maize: 1.5; and rapeseed and agrimony: 1.0. After determining the production of straw for each province, its energy value was determined. It was assumed that 13 GJ can be obtained from one ton of straw, and the efficiency of the devices is 80% [57]. The theoretical potential means that all straw produced is used for energy purposes. However, due to the wide use of this raw material in agriculture for fodder and bedding for livestock [58], the technical potential was also calculated, which assumes the use of only the surplus for energy purposes, which is not used in the agricultural production process. Therefore, the technical potential of straw was calculated as the product of the surplus of straw produced in agriculture, the energy value of straw, and the efficiency of devices converting straw into energy. The surplus of straw was calculated as the difference between the total production of straw and its demand in agriculture. It was assumed that straw in agriculture is used in animal production for fodder and bedding purposes. The following annual requirements for bedding were adopted for the following animals: cattle—cows: 1 t/year; cattle—other: 0.5 t/year; pigs—sows: 0.5 t/year; pigs—other: 0.2 t/year; sheep: 0.2 t/year; horses: 0.9 t/yr. In the breeding of some animals, straw is also used for fodder purposes. Therefore, the following standards of straw consumption for individual animals were adopted: cattle—cows: 1.2 t/year; cattle—other: 0.6 t/year; sheep: 0.2 t/year; and horses: 0.8 t/year [52]. After determining the total surplus of straw, its energy value was estimated, assuming the energy value at the level of 13 GJ/t and the efficiency of the devices at 80% [57,58].

The theoretical potential of hay was estimated as the product of meadows and pastures, the average yield of hay from meadows and pastures, the energy value of hay, and the efficiency of devices converting hay into energy. The area of meadows and pastures was determined on the basis of data from the Central Statistical Office in Poland [11]. The average yield of hay from meadows and pastures was assumed to be 4 t/ha [57]. The energy value was assumed at the level of 13.4 GJ—humidity 15% [53], and equipment efficiency 80% [47]. However, due to the fact that hay from meadows and pastures is widely used in agricultural production as feed for livestock, only a small part of it can be used for energy purposes. Therefore, the technical potential was also calculated, which takes into account the needs of agriculture for this raw material. The technical potential was estimated as the product of the area of meadows and pastures, the coefficient of using the average yield of hay from meadows and pastures for energy purposes, the energy value, and the efficiency of devices converting hay into energy. According to Kowalczyk-Juśko [52], on the national scale, the coefficient of using hay from meadows and pastures for energy purposes is at the level of 5–10%. Due to the lack of detailed information on the use of permanent grassland in individual voivodeships, it was assumed that 7.5% of the available area could be used for energy purposes. The energy value was assumed at the level of 13.4 GJ—humidity 15% [53], and equipment efficiency 80% [47].

The theoretical potential of plants intended specifically for energy purposes was estimated as the product of land suitable for cultivation of plants for energy purposes, average yields of selected energy plants, energy value, and the efficiency of devices converting the raw material into usable energy. Fallow land was taken into account as land that is suitable for cultivation. Data on fallow land was taken from the Central Statistical Office [11] for each voivodeship. The average yield of energy crops was assumed at the level of 8 t/ha [52]. The energy value of biomass from energy crops was assumed at the level of 18 GJ/t, and the efficiency of devices processing biomass into energy was 80% [54]. Due to the fact that it is not possible to allocate the entire area for energy purposes, the technical potential is 50% of the theoretical potential [21].

The theoretical potential of wood from orchard care was estimated as the product of the area of orchards, the yield of waste wood from 1 ha of orchards, the energy value of wood, and the efficiency of devices converting biomass into energy. Data on the area of orchards were taken from the Central Statistical Office in Poland [11]. The yield of wood from one hectare of orchards was assumed at the level of 0.35 t [54], the energy value of 1 ton of biomass from orchards at the level of 9.9 GJ, and the processing efficiency is 80% [53]. Due to the fact that this type of biomass is not used in agriculture, the technical potential is equal to the theoretical potential.

Theoretical potential from by-products from livestock farming was estimated as the product of livestock size in large conversion units (LU), biogas production index (m³/DJP), methane content in biogas (% volume), the energy value of biogas (MJ/m³), and the efficiency of devices converting biogas into energy. Data on the number of livestock stocks were taken from the Central Statistical Office of Poland [11]. The stock of individual livestock was converted into LU according to the following indices: cattle—0.8; pigs—0.3; poultry—0.02 [53]. The volume of biogas production for individual farm animals was estimated according to the following indicators: cattle—1.5; pigs—1.0; poultry—3.75 [52]. The share of methane in biogas was assumed at 57%, the energy value of biogas is 36 MJ, and the efficiency of the devices is 80% [53]. Due to the fact that natural fertilizers from livestock are widely used in agriculture (manure), there is a need to estimate the technical potential that takes these needs into account. In order to estimate the technical potential, the theoretical potential was reduced by the demand for nitrogen in agriculture. The technical potential was calculated by determining the structure of individual fractions of natural fertilizers (manure, liquid manure, slurry, and straw manure) and determining the nitrogen content in them (

Table 2. Structure of individual fractions of natural fertilizers (in %) and their nitrogen content (kg N/t).

Type of Breeding	Manure		Liquid Manure		Slurry		Straw Manure
	%	kg N∙t−1	%	kg N∙t−1	%	kg N∙t−1	%	kg N∙t−1
Cattle	27	6.39	5	4.61	41	5.3	27	9.74
Pig	8	11.09	5	3.08	84	4.31	3	2.41
Poultry	0	0	0	0	3	6.18	97	19.86

Source: [53].

). The demand for nitrogen in crop production is 85 kg/ha [53]. On the basis of the estimated values, the size of the technical potential possible to be used for energy purposes was determined.

3. Results

The analyses carried out for the purposes of the study show that the theoretical potential of biomass of agricultural origin in Polish voivodships in 2020 was at the level of 17,531.46 Ktoe. Among the analyzed sources of biomass of agricultural origin, the highest share was characterized by straw being a residue from cereal cultivation, and it constituted 55.47% (9723.88 Ktoe). The next largest sources of biomass of agricultural origin were natural fertilizers resulting from animal husbandry and hay from meadow pastures, accounting for 22.74% and 18.71% of the total potential, respectively. On the other hand, energy crops grown on fallow land and residues from orchard cuttings accounted for the smallest share in the total potential of biomass of agricultural origin, 2.95% and 0.13%, respectively. Taking into account individual voivodeships of Poland, the potential of biomass of agricultural origin was in the range from 456.67 to 2564.05. The average was 1095.72 Ktoe. The greatest potential was in the Wielkopolskie (2564.05 Ktoe), Mazowieckie (2325.82 Ktoe), and Lubelskie (1361.58 Ktoe) voivodeships. These voivodeships together accumulate 35.65% of the total potential of biomass of agricultural origin. On the other hand, the lowest theoretical potential of biomass of agricultural origin was found in the following voivodeships: Świetokrzyskie (456.67 Ktoe), Lubuskie (494.11 Ktoe), and Śląskie (517.07 Ktoe). The share of these voivodeships in the general potential is only 8.37% (

Table 3. Theoretical potential of biomass of agricultural origin in Polish voivodeships in 2020.

Voivodeship	Biomass of Agricultural Origin—Theoretical Potential
	The Potential of Cereal Cultivation—Straw	Potential from Meadows and Pastures—Hay	The Potential of Fallow Land— Energy Crops	Potential from Orchards—Residues from Pruning Orchards	The Potential of Animal Husbandry— Natural Fertilizers	Total
	Ktoe
Dolnośląskie	828.51	141.98	23.55	0.62	104.40	1099.05
Kujawsko-Pomorskie	937.24	98.20	12.95	0.43	271.23	1320.04
Lubelskie	902.36	212.62	42.54	4.81	199.26	1361.58
Lubuskie	252.43	122.67	26.19	0.42	92.39	494.11
Łódzkie	690.92	144.06	36.89	2.73	307.63	1182.22
Małopolskie	254.71	227.31	20.55	0.88	88.34	591.80
Mazowieckie	958.79	506.26	78.59	7.39	774.79	2325.82
Opolskie	591.14	44.53	5.30	0.09	99.08	740.15
Podkarpackie	324.42	221.60	47.96	0.77	83.88	678.64
Podlaskie	436.53	414.89	16.88	0.32	345.24	1213.86
Pomorskie	503.05	135.88	21.94	0.22	147.28	808.37
Śląskie	267.73	86.01	33.71	0.15	129.47	517.07
Świętokrzyskie	195.91	109.85	35.27	2.78	112.86	456.67
Warmińsko-Mazurskie	528.95	379.93	42.76	0.31	226.69	1178.64
Wielkopolskie	1474.87	240.03	28.86	1.00	819.28	2564.05
Zachodniopomorskie	576.32	194.42	42.89	0.63	185.13	999.39
Total	9723.88	3280.24	516.84	23.55	3986.95	17,531.46
Share %	55.5	18.7	3.0	0.13	22.7	100.00

Source: Author’s own elaboration.

).

The analyzed sources of biomass are widely used in agriculture—straw from cereal crops as fodder and bedding for livestock; hay from meadows and pastures as animal feed; and by-products from animal husbandry as a natural fertilizer used on agricultural land. Therefore, the estimated theoretical potential cannot be fully used for energy purposes. Therefore, the technical potential was calculated, taking into account the needs of agriculture for straw, hay, and natural fertilizers. The calculated technical potential is only 39.9% of the theoretical potential. The highest share in the technical potential of biomass of agricultural origin is straw—92.4%. On the other hand, other sources account for a much smaller share, i.e., energy crops grown on fallow land—3.7%; hay from meadows and pastures—3.5%; and residues from cutting orchards—0.3%. There was no potential to be used for energy purposes in the field of residues from livestock farming. In addition, in the field of natural fertilizers, there were shortages for their demand in agriculture. In the analyzed voivodships, the technical potential ranged from 39.88 Ktoe to 912.76 Ktoe. The average was 436.68 Ktoe. The highest technical potential was recorded in the following voivodeships: Wielkopolskie (912.76 Ktoe), Dolnośląskie (788.07 Ktoe), and Lubelskie (763.48 Ktoe). The total share in the general potential of these voivodeships is 35.27%. On the other hand, the smallest potential of biomass of agricultural origin was recorded in the following voivodships: Podlaskie (39.88 Ktoe), Świętokrzyskie (147.06 Ktoe), and Małopolskie (190.27 Ktoe). In total, these voivodeships accumulate only 5.40% of the total technical potential of biomass of agricultural origin (

Table 4. Technical potential of biomass of agricultural origin in Polish voivodships in 2020.

Voivodeship	Biomass of Agricultural Origin—Technical Potential
	The Potential of Cereal Cultivation—Straw	Potential from Meadows and Pastures—Hay	The Potential of Fallow Land—Energy Crops	Potential from Orchards—Residues from Pruning Orchards	The Potential of Animal Husbandry— Natural Fertilizers	Total
	Ktoe
Dolnośląskie	765.03	10.65	11.77	0.62	0.00	788.07
Kujawsko-Pomorskie	667.16	7.36	6.47	0.43	0.00	681.44
Lubelskie	721.45	15.95	21.27	4.81	0.00	763.48
Lubuskie	204.70	9.20	13.10	0.42	0.00	227.42
Łódzkie	434.12	10.80	18.44	2.73	0.00	466.10
Małopolskie	162.07	17.05	10.28	0.88	0.00	190.27
Mazowieckie	374.00	37.97	39.30	7.39	0.00	458.66
Opolskie	516.54	3.34	2.65	0.09	0.00	522.61
Podkarpackie	274.76	16.62	23.98	0.77	0.00	316.13
Podlaskie	0.00	31.12	8.44	0.32	0.00	39.88
Pomorskie	360.68	10.19	10.97	0.32	0.00	382.16
Śląskie	194.90	6.45	16.86	0.15	0.00	218.36
Świętokrzyskie	118.41	8.24	17.63	2.78	0.00	147.06
Warmińsko-Mazurskie	280.27	28.50	21.38	0.31	0.00	330.46
Wielkopolskie	879.33	18.00	14.43	1.00	0.00	912.76
Zachodniopomorskie	505.41	14.58	21.44	0.63	0.00	542.06
Total	6458.84	246.02	258.42	23.65	0.00	6986.92
Share %	92.4	3.5	3.7	0.3	0.0	100.0

Source: Author’s own elaboration.

).

The total theoretical potential of Polish voivodeships, derived from straw obtained from cereal crops, amounted to 9723.88 Ktoe. In individual voivodeships, the potential from this source ranged from 195.91 to 1474.87 Ktoe. The average was 607.74 Ktoe. The following voivodeships were characterized by the highest potential: Wielkopolskie (1474.87 Ktoe), Mazowieckie (958.79 Ktoe), and Kujawsko-Pomorskie (937.24 Ktoe). On the other hand, the smallest potential was recorded in the following voivodships: Świętokrzyskie (195.91 Ktoe), Lubuskie (252.43 Ktoe), and Małopolskie (254.71 Ktoe) (Table 3). Taking into account the demand for straw in agriculture, the technical potential of this source was estimated at 6658.84 Ktoe, which is 66.42% of the theoretical potential. In the analyzed voivodships, the values of the potential from this source ranged from 0.00 Ktoe to 879.33 Ktoe. The average was 403.68 Ktoe. The highest technical potential from this source was recorded in the following voivodeships: Wielkopolskie (879.33 Ktoe), Dolnośląskie (765.03 Ktoe), and Lubelskie (721.45 Ktoe). On the other hand, such voivodships as Podlaskie (0.00 Ktoe), Świętokrzyskie (118.41 Ktoe), and Małopolskie (162.07 Ktoe) were characterized by much lower potential (Table 4).

The total theoretical potential of Polish voivodeships, derived from hay obtained from meadows and pastures, amounted to 3280.24 Ktoe. In individual voivodeships, the potential from this source ranged from 44.53 to 506.26 Ktoe. The average was 256.27 Ktoe. The following voivodships were characterized by the highest potential: Mazowieckie (506.26.82 Ktoe), Podlaskie (414.89 Ktoe), and Warmińsko-Mazurskie (379.93 Ktoe). On the other hand, the lowest potential was recorded in the following voivodeships: Opolskie (44.53 Ktoe), Śląskie (86.01 Ktoe), and Kujawsko-Pomorskie (98.20 Ktoe) (Table 3). Taking into account the demand for hay in agriculture, the technical potential of this source was estimated at 246.02 Ktoe, which is 7.50% of the theoretical potential. In the analyzed voivodeships, the values of the potential from this source ranged from 3.34 to 37.97 Ktoe. The average was 15.38 Ktoe. The highest technical potential from this source was recorded in the following voivodships: Mazowieckie (37.97 Ktoe), Podlaskie (31.12 Ktoe), and Warmińsko-Mazurskie (28.50 Ktoe). On the other hand, the following voivodships were characterized by much lower potential: Opolskie (3.34 Ktoe), Śląskie (6.45 Ktoe), and Kujawsko-Pomorskie (7.36 Ktoe) (Table 4).

The total theoretical potential of Polish voivodeships, derived from energy crops grown on fallow land, amounted to 516.84 Ktoe. In individual voivodships, the potential from this source ranged from 5.30 to 78.59 Ktoe. The average was 32.30 Ktoe. The following voivodships were characterized by the highest potential: Mazowieckie (78.59 Ktoe), Podkarpackie (47.96 Ktoe), and Zachodniopomorskie (42.89 Ktoe). On the other hand, the smallest potential was recorded in the following voivodeships: Opolskie (5.30 Ktoe), Kujawsko-Pomorskie (12.95 Ktoe), and Podlaskie (16.88 Ktoe) (Table 3). Taking into account that not all fallow land is suitable for the cultivation of energy crops, the technical potential of this source was estimated at 258.42 Ktoe, which is 50.00% of the theoretical potential. In the analyzed voivodships, the values of the potential from this source ranged from 2.65 Ktoe to 39.30 Ktoe. The average was 16.15 Ktoe. The highest technical potential from this source was recorded in the following voivodeships: Mazowieckie (39.30 Ktoe), Podkarpackie (23.98 Ktoe), and Zachodniopomorskie (21.44 Ktoe). On the other hand, the following voivodeships were characterized by much lower potential: Opolskie (2.65 Ktoe), Kujawsko-Pomorskie (6.47 Ktoe), and Podlaskie (8.44 Ktoe) (Table 4).

The total theoretical potential of Polish voivodeships, derived from residues from pruning orchards, amounted to 23.55 Ktoe. In individual voivodeships, the potential from this source ranged from 0.09 to 7.39 Ktoe. The average was 1.47 Ktoe. The following voivodeships were characterized by the highest potential: Mazowieckie (7.39 kote), Lubelskie (4.81 Ktoe), and Świętokrzyskie (2.78 Ktoe). On the other hand, the lowest potential was recorded in the following voivodeships: Opolskie (0.09 Ktoe), Śląskie (0.15 Ktoe), and Pomorskie (0.22 Ktoe) (Table 3). Due to the fact that this type of biomass is not used directly or indirectly in agriculture for food production, the technical potential from this source is the same as the theoretical potential.

The total theoretical potential of Polish voivodeships, derived from natural fertilizers resulting from livestock breeding, amounted to 3986.95 Ktoe. In individual voivodships, the potential from this source ranged from 83.88 to 819.28 Ktoe. The average was 249.18 Ktoe. The following voivodeships were characterized by the highest potential: Wielkopolskie (819.28 Ktoe), Mazowieckie (774.79 Ktoe), and Podlaskie (345.24 Ktoe). On the other hand, the lowest potential was recorded in the following voivodeships: Podkarpackie (83.88 Ktoe), Małopolskie (88.34 Ktoe), and Lubuskie (92.39 Ktoe) (Table 3). Due to the fact that this type of biomass of agricultural origin is widely used in plant production, no technical potential that could be used for energy purposes was recorded in any of the analyzed voivodeships.

4. Discussion

In accordance with the main objective of the research, the potential of agricultural biomass and the possibility of its use for energy purposes in Polish voivodeships were assessed. In the course of the research, the potential from agricultural biomass was estimated, what part of the estimated potential could be used for energy purposes, and the dominant sources of agricultural biomass in Poland were indicated. The conducted research included the analysis of five sources of agricultural biomass, i.e., straw from cereal cultivation, hay from meadows and pastures, plants intended specifically for energy purposes grown on fallow land (willow), wood from pruning orchards, and by-products from livestock farming (natural fertilizers).

The research shows that agricultural biomass in Poland may be a promising source of renewable energy, as its significant potential has been identified. Therefore, one should agree with Saleem [20] that biomass can be a competitive source of renewable energy. Moreover, by exploiting the existing potential, as underlined by Gyamfi et al. [28], emissions of undesirable pollutants into the atmosphere can be reduced, and, as indicated by Liu et al. [25], energy security can be increased by limiting potential energy shortages. In addition, agreeing with Sherwood [24], the use of agricultural biomass for energy purposes may be an important factor in implementing the assumptions of the circular economy currently promoted by the European Union. Finally, also agreeing with Cintas et al. [26], the use of the existing potential can contribute to achieving the climate goals assumed by the European Union policy and mitigating the effects of current land use.

However, it should be remembered that, as indicated by Sadowski [1] and Bański [3], the basic task of agriculture is to ensure the appropriate amount of food supply, which is achieved thanks to agricultural production [2]. This production is carried out with the use of biomass for fodder, bedding, and fertilization purposes. Therefore, as indicated by Gavrilescu [49], without conflict with the agricultural sector, only the part of biomass that is not used in agricultural (plant and animal) production can be used for energy purposes.

For this reason, in addition to the theoretical potential, the technical potential was also estimated, which takes into account the use of only that part of biomass that is not used in agricultural production. Therefore, there are differences in the possibility of using different sources of biomass for energy purposes. The estimated theoretical potential indicates that the dominant sources of agricultural biomass in Poland are straw from cereal cultivation, hay from meadows and pastures, and by-products from livestock breeding (natural fertilizers). This is in line with the Energy Policy of Poland until 2040, in which, in the field of biomass, the main hopes are placed on the use of biomethane from animal production produced in agricultural biogas plants (in transport, power engineering) and solid biomass (in heating and power engineering) [41]. However, after taking into account the needs for biomass in agricultural production (plant and animal) in the estimated theoretical potential, it is economically justified to use only straw from cereal crops for energy purposes. Similar conclusions were also drawn by Knapek et al. [29], who indicated that the main biomass resources that can be used for energy purposes will be straw from agricultural production. The research conducted by Vaish et al. [30] also shows great opportunities for the use of post-harvest residues for energy purposes, which are not used in agricultural production and are often treated as waste, thrown away or burned in the fields. Liu et al. [25] and similarly, Scarlat et al. [31] and Hamelin et al. [32], conducting their research in the European Union countries, also indicated that straw from cereal crops can be used for energy purposes. In addition, extensive and detailed research conducted by Pudełko [53] in the field of various types of biomass (by-products from agriculture, waste from forestry, nature conservation, and municipal and industrial waste) also proved that straw has the greatest energy potential. Research by scientists Demirel et al. [34], Mohammed et al. [35], and Odavić et al. [36], conducting their research outside Europe (in Sudan, Ghana, and Serbia), also noticed great opportunities to use agricultural residues for energy purposes. The identified straw surplus potential can have positive climate impacts if used to support coal-fired power plants, as highlighted by Cintas et al. [26].

In opposition to the research of Knapek et al. [29], only a small potential was identified in terms of the possibility of using biomass from permanent grassland for energy purposes due to the high demand in animal production as fodder. Due to the small area of fallow land, unlike the authors mentioned above, no significant potential for the use of purposely cultivated energy crops for energy purposes has been identified. In contrast to the study by Mahmood et al. [37], after taking into account the needs related to fertilization of fields, no potential that can be used for energy purposes from by-products resulting from farm animal breeding (natural fertilizers) has not been identified. In the case of greater use of by-products from livestock farming (natural fertilizers), there is a chance of their greater use if post-fermentation fractions start to be used for fertilization purposes, but there are no appropriate practical and legal solutions.

5. Conclusions

Agricultural biomass in Poland has a good chance of development as a source of renewable energy. This is confirmed by the fact that Poland is a country with a strong agricultural sector, which is indicated by the way the country’s area is used, the structure of employment, and the share of this sector in the gross domestic product of the country. In addition, on the basis of the research, a significant energy potential of this source has also been identified. However, it is best to use surplus biomass for energy purposes so as not to disturb the natural processes of agricultural production. Taking these needs into account, the potential that can be used for energy purposes is at the level of 6986.92 Ktoe, constituting 39.9% of the theoretical potential. Among the analyzed sources of agricultural biomass, straw from plant production turned out to be dominant. Straw amounts to 6458.64 Ktoe and constitutes 92.4% of the entire estimated technical potential of agricultural biomass. Other sources of agricultural biomass included in the analysis account for less than 8% altogether: hay from permanent grassland—3.5%; energy crops grown on fallow land—3.7%; residues from the results of orchards—0.3%. However, the potential that could be used for energy purposes derived from by-products from animal production has not been identified.

Straw is a promising source of renewable energy, which is most often used as biofuel in the combustion process. Straw is considered to be an ecological source of energy because grain absorbs more CO₂ from the atmosphere during the growing season than it produces later in the process of its combustion. On the other hand, the ash formed in the combustion process can be used as plant mineral fertilizer due to the high content of calcium and potassium oxides. In addition, the use of this raw material for energy purposes makes it possible to strengthen the agricultural sector in the economic aspect, especially when the prices of the raw materials produced are low, and it is difficult to obtain a satisfactory level of income. In Poland, installations using this source of biomass are becoming more and more popular. However, the importance of this source in the future energy market will depend mainly on the future policy of the European Union in the field of energy from renewable sources, as well as further development of technology, market situation, and applied incentives.

Although a significant theoretical potential (22.3% of the total theoretical potential) has been identified in the field of natural fertilizers from animal production, due to their extensive use in plant production as fertilizer, no surpluses have been identified that could be used for energy purposes. However, observing the changes taking place in Polish agriculture regarding the storage and management of natural fertilizers, one can expect an increase in the importance of renewable energy from agricultural biogas plants in the near future.

In conclusion, it should be emphasized that the use of biomass residues from agriculture for energy purposes is advisable due to the possibilities of reducing greenhouse gas emissions and can be done without negative impact on the environment—provided that sustainable agriculture is conducted. If it is conducted in an unsustainable manner, excessive development of one branch of the economy will result in the disturbance of another.