Decentralized Biogas Technology of Anaerobic Digestion and Farm Ecosystem: Opportunities and Challenges

Abstract

Long-term economic and environmental concerns have resulted in a great amount of research on renewable sources of biomass and bioenergy to replace fossil fuels in the past decades. Decentralized biogas technology is one of the most potential technologies of biomass and bioenergy by using agricultural waste materials (e.g., animal manure, crop straw, and by-products from food industries) as feedstocks. By-products from biogas production, called digestate, are nutrient rich, which could potentially be reused as green fertilizers in agriculture, thereby providing a sustainable substitute for synthetic fertilizers for farm ecosystem. Thus, the biogas production of anaerobic digestion is win-win option for livestock and crop producers to address issues of waste management and energy supply, and to avoid contamination of surface and ground waters and emissions of odors and greenhouse gases. In this paper, we review biogas production technology and then evaluate environmental effects of digestate used as fertilizer. Finally, we discuss issues of deployment of decentralized biogas technology for farm ecosystem. Economic and technological barriers still exist for large scale deployment of biogas technology in rural region. Two national scale deployments in China and Nepal showed that the operational status of biogas digesters is not optimal and up to 50% of plants are non-functional after a short operation period regardless of the social and economic factors. Main barriers are a wide variation of feedstocks and environmental conditions (e.g., temperature) over space and time. It becomes clear that the experimental conditions of the pilot plants need to be adjusted and calibrated to the local feedstocks and climate. Also, more research needs to be done in cold fermentation technology. Thus, collaboration of all relevant designers, farmers, stakeholders, and regulators is proposed as the way forward, particularly as their complexity has been identified as the major hurdle to the implementation of decentralized biogas production, which can deliver beneficial synergies for the decentralized biogas production in rural region responsible for food production and waste management.

Effect of Liquid Digestate on Agricultural Soil – I: Growth Dynamics of Zea mays Plant

“…Furthermore, there was a significant difference (P<0.05) in biomass yield of Zea mays plant concerning the concentration (%) and mode of application of the liquid digestate respectively. This suggests that the concentration and mode of application of the liquid digestate (as organic fertilizer) may have significantly influenced biomass yield of the crop with time [27,28,29,30,31,32,41]. It also suggests that the two-time mode of digestate application (TTDA) may have promoted the growth of the Zea mays plant better than the one-time digestate application (OTDA) treatment mode.…”

“…Moreover, the presence of macro and micro elements in most digestates make them excellent form of fertilizer when applied correctly [18,19,20,21,22,23,24,25]. In order to fully exploit biogas digestate in crop production, it is necessary to test its performance in the soil-plant ecosystem by investigating its effect on different soil types, plant growth and greenhouse gas (GHG) emission [26,27,28,29,30,31,32]. As organic farming prohibits the use of synthetic fertilizers on agricultural soils, digestate from anaerobic digestion of organic matter seem to offer a better alternative to these as well as undigested organic matter, which are sometimes used [24,33,34,35,36].…”

Freeze Granulated Zeolites X and A for Biogas Upgrading

“…Biogas offers a sustainable fuel to the environment as it contributes to low carbon emissions during its combustion. The raw biogas obtained from an anaerobic digester mainly consist of CH 4 with 40-45% CO 2 including a minor content of impurities, such as water, siloxanes, ammonia and hydrogen sulfide [1,2]. Great efforts have been made in the biogas separation and purification technologies to procure biomethane with a low energy footprint [3,4].…”

Comparison of pretreatment methods that enhance biomethane production from crop residues - a systematic review

“…CR are largely at the lower end of the BMP spectrum because of high lignocellulose content. Lignocellulose limits degradation by anaerobic bacteria (Wang, 2014;Achinas, 2017). CR are heterogeneous in nature limiting their use as feedstock for AD (Horváth et al, 2016).…”