**1. Introduction**

Agriculture is the predominant occupation of Thai people despite the constant industrial growth occurring in many parts of Thailand. In terms of agricultural lands, Thailand is also one of the largest countries in the world, especially in Asia [1]. Thailand is one of the fastest growing and energy-intensive economies in South-East Asia. Fifty percent of the total energy demand required to meet the present growth is met only through import [2]. Being a country with plenty of agricultural and energy crops, Thailand has the potential to fulfill the energy needs through biogas production [3]. Anaerobic digestion technology has emerged as one of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the best technologies for the production of biogas [4]. Because of the concerns regarding energy security and environmental impact of fossil fuels, utilization of renewable energy is signifi‐ cantly increasing which will leads to the upgradation of living standards of people [5].

is different from other biofuels like biohydrogen, bioethanol, and biodiesel which uses only carbohydrates and lipids. Biogas is produced from all the convertible biomass macromolecules

Grass Silage for Biogas Production http://dx.doi.org/10.5772/64961 155

AD is a collection of process achieved through bacteria that convert organic materials into biogas through four different stages (**Figure 1**) including hydrolysis, acidogenesis, acetogenesis, and methanogenesis [8, 9]. Organic matters are broken down step by step through these four stages towards methane production path. The complex macromolecules and components (carbohydrates, lipids, and proteins) available in organic matter are converted into simple sugars, long-chain fatty acids, and amino acids through first stage so-called hydrolysis. And second stage (acidogenesis) in turn converts these soluble micromolecules into volatile fatty acids, acetic acid, CO2, and H2. Third stage of acetogenesis converts the volatile fatty acids into more acetic acid, CO2, and H2S gas. The final stage of methanogenesis has the capability to generate methane by using the CO2 and H2S gas otherwise the acetic acid produced from either second or third stages [8, 9]. Thus, the AD process, if improperly managed, would become unstable and result in reduced biogas production. An overall review and assessment of AD techniques for biogas production and relevant research progress are necessary and imperative

Compared with other feedstocks, grass has suitable and promising characteristics as energy crop for biogas production. Because of its assurance on availability of throughout year and conservation, ensilage or haylage are indisputable. Typically, compacting to extrude sheltered air and a plastic coverage is enough for conservation of fresh grass [10]. In general, the usage of grassland as a renewable source of energy during biogas production will provide consid-

under anaerobic conditions [8, 9].

**Figure 1.** Flow diagram of the anaerobic digestion process.

for further biogas development.

**3. Grass: energy crop**

Energy crops are the type of plants cultivated as raw materials for biogas production. Agri‐ cultural lands in Thailand are well suitable for growing annual crops. Usually, temperature is warm to hot weather year‐round in Thailand. The highest temperature recorded is generally during summer in the months of March till May. Most of the region receives an average rainfall of around 1100 mm. The annual crops can be used as an energy crop or raw material for biogas plant [1]. Among energy crops, grasses which belong to perennial crops are suitable due to their fastest growing rates even in infertile land, low cultivation costs, higher accessibility, consumption of whole plants, and lower environmental impacts when compared to other plants [6]. Some grass species are reported to have large amount of fibers and carbohydrates from which biogas can be produced. Many such types of grasses are popularly growing in Thailand [3, 7]. Grass substrates are converted to silage to be used as feedstock for anaerobic digestion. Energy production from silage has also attracted much interest in recent years. In the United States, perennial grasses have been stored as biomass to produce biofuels. This chapter illustrates the basic concepts of anaerobic digestion and addresses the overview of potential of grass as raw material for biogas production advance silage preparations and utilization for efficient biogas production with several digestion methods including dry and wet fermentation processes, monodigestions, and co‐digestions, along with environmental impact assessment. Consequently, the aim of this chapter was to provide an overview of how to efficiently utilize the grass silage for biogas production and helpful to reduce greenhouse gas effect with environmental benefits.
