**Utilization of Permanent Grassland for Biogas Production**

Pavel Fuksa1, Josef Hakl1, Zuzana Hrevušová1, Jaromír Šantrůček1, Ilona Gerndtová2 and Jan Habart3 *1Department of Forage Crops and Grassland Management, Czech University of Life Sciences, Prague 2Research Institute of Agricultural Engineering 3Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences, Prague Czech Republic* 

#### **1. Introduction**

170 Modeling and Optimization of Renewable Energy Systems

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Permanent grasslands represent undoubtedly an inseparable part of landscape, which has historically both agriculture and environmental importance. Considering restricting agriculture-food-processing production, especially in Central and Eastern European countries, the main aim of European policy is to support mainly environmental function of permanent grasslands. To fulfil non-productive function of permanent grasslands, there is the base of their utilization and harvest of biomass. Therefore, agriculture is also focused on non-food processing production where the first place is taken by energy production.

This chapter is dealing with utilization of permanent grasslands for energy production and their energetic balance. The main attention deals with a particular way of production of biogas, which is the most applied method as far as energy production of this vegetation in Europe is concerned. The production of biomass for energy, as well as traditional forage produce, cannot omit functions of permanent grasslands. Therefore, a part of the chapter is also focused on biological and environmental aspects of permanent grasslands. It is not possible to incorporate all related topics in their entirety because of limited scope of the chapter. The aim of this chapter is to give general knowledge with emphasis on reciprocal coherence of mentioned issues. Detailed information can be found in cited literature.

#### **2. Importance of permanent grassland**

Permanent grasslands are important parts of natural landscape, as well as, element of management of agricultural land not only in the Europe territory. Grassland covers approximately 3.4 109 ha, i.e. 69 % of the world's agricultural area or 26 % of total land area. In Europe, grasslands also cover a considerable amount of landscape. Currently they represent almost 38 % of agricultural land area. Area in the Czech Republic has been expanding over last few years. At present grasslands cover over 23 % of agricultural land area (Food and Agriculture Organization Statistic [FAOSTAT], 2011).

Utilization of Permanent Grassland for Biogas Production 173

The usage of biomass for animal nutrition is still dominant way of its utilization, but in the recent period the importance of this traditional relation has been reduced. The main reasons for this can be considered reducing the quantity ruminants, especially in the countries of Central and Eastern Europe. As a result of increasing milk and meat productivity of animals, in suitable regions there is an increase of amount of fodder being produced from arable land (legume-grass mixture, maize). Because of this and other reasons (for example political and financial support for renewable energy) there has been in last 10 – 15 years significant increase in usage of biomass produced from permanent grasslands for alternative purposes (Hohenstein & Wright, 1994; Prochnow et al., 2009a,

According to Prochnow et al. (2009b), the grassland biomass is suitable in many ways for producing energy. Currently it is used in practice as a feedstock for biogas production and as solid biofuel for combustion. Future pathways can include the production of lignocellulosic bioethanol, synthetic biofuels or synthetic natural gas. Feedstock from grassland will also be used as raw material for the bio-industry within Green Biorefineries

If suitable management of permanent grasslands regarding productive and nonproductive functions stays the same, the change in how the final product is being used will not have a negative impact on farming of permanent grasslands. Permanent grasslands also have an important function in relation with arable land. Ruminants transfer the biomass through digestion and partially use it for their need. The remaining 35 – 50 % of organic matter is excreted in form of excrements. Organic matter in form of farm fertilizer is then used primarily on arable land and there it is important factor contributing to its fertility. When we utilize grass biomass for energy, however, loss of organic matter is higher. Biogas fermentation can degrade cellulose to an extent of about 80 % (Ress et al., 1998). Usage of biomass for direct combustion leads to 100 % loss of organic matter. Energy utilization of biomass can therefore lead to reduction in return of organic matter into soil, in comparison with traditional system, where fodder is utilized

With reduction of return of the organic matter into the soil, there can be disruption in organic balance of the agricultural system, which can lead to number of negative consequences (reduction in fertility of the soil, increase in leaching nutrients into the underground water, increased hazard of erosion etc.). It is necessary to reduce hazards to arable lands such as these by applying effective countermeasures, for example by increasing the share of legumes in crop rotation or by growing catch crops (Brant et al., 2011). The risk is not significant in permanent grasslands. The root system of the plants creates sufficient amount of organic matter inside the soil, so it is not necessary to fertilize them organically at

Permanent and semi-natural grassland are very important not only as a source of fodder, but they also play a significant role in environment (Stypiński et al., 2009). These non-

productive functions of permanent grasslands interfere in different fields such as:

2009b; Rösch et al., 2009).

by ruminants.

a regular base.

**3.2 Non-productive functions** 

(Kromus et al., 2006, as cited in Prochnow et al., 2009b).

Permanent grassland is defined as a land used permanently (for five years or more) for herbaceous forage crops, either cultivated or growing wild (FAOSTAT, 2011). Under favourable conditions, the grass species prevail in grasslands. However varied ecological conditions allow expansion of large amount of different plant species, where legumes are, for many reasons, very important. The plant composition is the result of interaction of ecological factors of placement and the methods of cultivation. The mediation of succession, such composition of natural species is created on sites that in given ecological conditions and specific way of utilization thrives the best. Throughout the years this balance is also created on newly founded stands seeded with mix of grasses and legumes.

Depending on place of origin we can discern between two basic types of permanent grasslands:


Permanent grasslands belong to agricultural systems with very high environmental value. They are among the most biologically active and most productive vegetation types with fast cycle of growth and high capability of transferring chemical elements in biosphere. Their importance comes from two key aspects: productive and non-productive functions.
