Viola Pinky Harumita, Siti Nafi'ah, Rizki Maulida, Risma Novia Safitri, Shofia Nur Areza, Sundahri*)
Study Program of Agrotechnology, Faculty of Agriculture, The University of Jember
*) Corresponding author: violapinki@gmail.com, nafikah587@gmail.com, riskimaulida27@gmail.com, rismasafitri608@gmail.com, shofia032@gmail.com, Sundahri.faparta@unej.ac.id
The utilization of rice straw as a substrate for biogas production within a circular agricultural energy system presents a promising opportunity for enhancing energy sustainability and agricultural resilience. Rice straw, generated as a by-product of rice cultivation, represents a substantial waste material, with estimates suggesting that its annual production exceeds 180 million tons in regions such as China alone (Kaldis et al., 2020). This vast quantity not only contributes to agricultural waste but also to environmental challenges like burning, which releases greenhouse gases and pollutants (Zaidi, 2021). Consequently, the integration of rice straw into anaerobic digestion systems for biogas production can facilitate effective waste management while generating renewable energy.
Biogas production from rice straw primarily hinges on anaerobic digestion (AD), a biological process that decomposes organic matter in the absence of oxygen. The efficiency of biogas yield can be significantly enhanced through various pretreatment techniques that target the cellulose and lignin structures of rice straw, which are typically resistant to microbial degradation. Recent studies have demonstrated that physical methods such as ultrasound treatment can increase biogas production by nearly fourfold compared to untreated straw (Gandhi et al., 2024). Furthermore, chemical pretreatments, including sodium hydroxide treatment, have been shown to improve methane yields substantially; for instance, one study reported an increase in methane production by 132% when rice straw was pretreated with a 3% NaOH solution (Matin & Hadiyanto, 2020). Similarly, microwave-assisted ammoniation treatments have also yielded positive results in enhancing biogas potential by improving the accessibility of organic substrates for microbial action (Liu et al., 2021).
The strategic co-digestion of rice straw with other biomass feedstocks offers an effective approach to optimizing biogas production. Research indicates that combining rice straw with nitrogen-rich materials, such as livestock manure or shrimp sludge, can enhance nutrient availability and maintain an optimal carbon-to-nitrogen (C/N) ratio crucial for microbial activity (Nam et al., 2022)Simioni et al., 2021). For instance, co-digestion of rice straw with shrimp sludge, adjusted to a C/N ratio of 25:1, yielded up to 29% higher biogas outputs than utilizing shrimp sludge alone (Nam et al., 2022). This co-digestion strategy thus not only amplifies biogas production but also promotes the recycling of nutrients back into the agricultural system, embodying the principles of a circular economy.
Moreover, the digestate produced from anaerobic digestion of rice straw serves as a valuable by-product that can be utilized as organic fertilizer, thereby augmenting soil quality and fertility. Nutrient-rich digestates derived from rice straw AD have been found to offer advantages in crop growth and yield when applied to agricultural lands, thus creating a symbiotic relationship between waste management and agricultural productivity (Jin et al., 2023). The digestion process not only reduces the environmental burden associated with rice straw disposal but also enables the return of essential nutrients to the soil, promoting sustainable agricultural practices.
Various regions are already implementing systems integrating biogas production from rice straw into their energy frameworks. For example, enhanced biogas facilities in countries like the Philippines harness rice straw along with animal manure to produce biogas, which can be used for energy-intensive post-harvest activities such as grain drying and milling (Gmez et al., 2024). Such systems provide local communities with renewable energy solutions while reducing reliance on fossil fuels. Furthermore, pilot studies in Egypt have shown significant energy outputs from the conversion of rice straw into biogas, with estimates suggesting that one ton of rice straw can generate approximately 1165 kWh of electricity (Said et al., 2020). These results underline the viability of rice straw as a crucial substrate for decentralized energy production initiatives globally.
While the energy potential of rice straw is promising, implications exist regarding the financial aspects involved in establishing and maintaining biogas facilities. A techno-economic analysis would be essential for assessing the feasibility of biogas production systems derived from rice straw and other agricultural residues. Research indicates that the adoption of innovative technologies, such as anaerobic co-digestion and optimized pretreatments, can lead to economically viable energy solutions while fostering sustainable practices in agricultural sectors (Suazo et al., 2023; Kabaivanova et al., 2022). Additionally, with growing regulatory frameworks aimed at enhancing renewable energy utilization, such systems could qualify for subsidies or financial support, aiding their widespread adoption.
Despite the advantages, certain challenges related to the large-scale implementation of biogas systems using rice straw should not be overlooked. Concerns about the consistency of feedstock quality, technological readiness, potential contamination from agricultural chemicals, and overall management of digestion processes must be carefully addressed to ensure long-term sustainability (Venslauskas et al., 2024; Ugwu et al., 2022). Further research focused on improving the robustness of biogas systems through innovative management practices and chemical treatments will be essential to harness the full potential of rice straw within a circular agricultural energy framework.
Overall, the integration of rice straw into biogas production systems holds the potential to transform waste into energy resources while contributing to environmental sustainability and energy security. The diverse pretreatment methodologies, opportunities for co-digestion, and avenues for nutrient recycling collectively underscore the multifaceted role rice straw can play in achieving renewable energy goals in agricultural landscapes. Embracing such strategies could significantly advance global efforts towards a more sustainable and circular economy in agriculture, promoting both energy efficiency and environmental stewardship.