Journal of Energy Bioscience 2024, Vol.15, No.4, 221-232 http://bioscipublisher.com/index.php/jeb 227 7 Environmental and Economic Impacts 7.1 Assessment of greenhouse gas emissions reduction The utilization of agricultural waste for biomass energy and organic fertilizer production has significant potential to reduce greenhouse gas (GHG) emissions. Various studies have demonstrated that recycling agricultural waste into biofertilizers and energy can mitigate GHG emissions effectively. For instance, the application of anaerobic digestate and olive pomace compost in organic farming systems has shown a reduction in total carbon emissions, with values of 63.9 and 67.0 kg of CO2 eq Mg-1, respectively (Diacono et al., 2019). Additionally, the use of industrial by-products such as fly ash, steel slag, and phosphogypsum in paddy fields has been found to mitigate methane and nitrous oxide emissions, contributing to lower overall GHG emissions (Kumar et al., 2020). Furthermore, the transformation of biomass waste into organic fertilizers has been shown to reduce life-cycle energy consumption and GHG emissions compared to traditional mineral fertilizers (Kyttä et al., 2020). 7.2 Improvement in soil health and crop productivity The application of organic waste-derived fertilizers has been shown to improve soil health and enhance crop productivity. Long-term field experiments have indicated that biogas residues and compost can significantly improve soil microbiological properties, such as substrate-induced respiration, potential ammonium oxidation, and nitrogen mineralization, leading to increased crop yields (Odlare et al., 2011). The use of compost and compost-based teas in horticultural systems has also been reported to enhance soil quality and plant health, providing essential nutrients and improving soil structure (Corato, 2020). Moreover, the application of biochar and raw agricultural waste as mulch has been observed to increase soil organic carbon, moisture, and nutrient content, resulting in a 36%-64% improvement in agricultural production (Dey et al., 2020). 7.3 Economic analysis of waste-to-energy and fertilizer systems Economically, the recycling of agricultural waste into energy and fertilizers presents several benefits. The production of bioenergy from organic waste in Chile, for example, has been estimated to meet 3.3% of the annual energy demand, highlighting the significant potential for energy security and resource efficiency (Ludlow et al., 2021). The use of recycled fertilizers also reduces the costs associated with landfilling, transportation, and the production of chemical fertilizers, while opening avenues for rural employment (Sharma et al., 2019). However, financial, technical, and institutional barriers, such as high investment costs and reliance on landfilling practices, need to be addressed to fully exploit these resources (Ludlow et al., 2021). Additionally, the economic value of recycled fertilizers can be influenced by the allocation methods used in life-cycle assessments, with economic allocation resulting in significantly lower impacts compared to mass allocation (Kyttä et al., 2020). In summary, the utilization of agricultural waste for biomass energy and organic fertilizer production offers substantial environmental and economic benefits, including GHG emissions reduction, improved soil health and crop productivity, and cost savings. However, overcoming existing barriers is crucial to realizing the full potential of these waste-to-energy and fertilizer systems. 8 Policy and Regulatory Framework 8.1 Overview of relevant policies and regulations The management and utilization of agricultural waste for biomass energy and organic fertilizer production are governed by various policies and regulations aimed at promoting sustainability and reducing environmental impact. In the European Union, for instance, there are stringent regulations that encourage the use of organic waste to produce fertilizers, aligning with the principles of a circular economy (Pajura et al., 2023). These regulations are designed to reduce the exploitation of natural resources and minimize the energy intensity of the fertilizer industry. Similarly, Spain and the Czech Republic have implemented policies that prioritize the reduction and valorization of agricultural waste biomass (AWB), driven by the circular economy and circular bioeconomy strategies (Duque-Acevedo et al., 2022). These policies are crucial in guiding the sustainable transformation of biomass waste into valuable products like organic fertilizers (Chew et al., 2019).
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