Evaluation of Biochar as an Additive in the Co-Composting of Green Waste and Food Waste

Abstract

Green waste (GW) represents 11% of municipal solid waste. Managing this waste is challenging due to its physicochemical variability, low density, and presence of hard-to-degrade lignocellulosic compounds. Composting is an alternative for GW transformation and valorization. However, due to the substrate characteristics, processing times are long, and the end product typically does not meet quality standards. Incorporating additives and co-substrates are operational strategies that contribute to overcoming these challenges. An essential step is the determination of a mixture’s composition that ensures synergistic effects on the process and end-product quality. This research assessed the effect of adding biochar (Bch) in the co-composting of GW and food waste (FW). A previously studied co-composting mixture (M) of GW, raw and processed FW, sawdust (Sd), and phosphoric rock (Pr) with four treatments by duplicate were assessed at the pilot scale: T1: 100% GW, T2: M1, T3: M2 + 2% Bch, y T4: M3 + 5% Bch. The results show that Bch treatments maintained the range of thermophilic temperatures for longer than the other two treatments (between four and five additional days), showing greater biological activity and better end-product hygienization. Likewise, in the Bch treatments, the hemicellulose and cellulose degradation improved compared to treatments without Bch by 33.9% and 23.3%, respectively, and nitrogen losses were reduced by up to 70%. Regarding the end product, adding a 2% dose of Bch allowed the highest fertility index compared to the other three treatments, showing its potential for agricultural use. This work demonstrates that adding biochar to FW and GW co-composting improves organic matter degradation rates, lignocellulosic degradation, and end-product quality.

Avances en investigación sobre el mejoramiento del compostaje de residuos verdes en países en desarrollo: experiencias desde Colombia

“…Considering the challenges to improve GW composting and the strategies identified in different contexts for its optimization, this article synthesizes the results of several studies developed in Colombia that have evaluated strategies for the improvement of GW composting. The investigations considered were developed by the authors of this paper, some of which are not published, while others have been presented in about 10 publications (4,9,(12)(13)(14)(15)(16)(17)(18)(19). This article addresses aspects such as the identification of the physicochemical characteristics of GW, the evaluation of the effect of the implementation of strategies to improve the process and product quality, and finally reflects on research perspectives to continue strengthening the implementation of composting in MSW management in developing countries such as Colombia.…”

“…doi: 10.25100/iyc.v26i1.13143 Advances in research on the improvement of green waste composting in developing countries: experiences from Colombia a Proportion of substrates with the best results in the experiment; b The treatment with the best results in the final product; N.A: No Additive; Bch: Biochar, N.R: Not reported, RFW: Raw Food Waste; PFW: Processed Food Waste; PR: Phosphate Rock; Sawdust; COT: Total Organic Carbon; TN: Total Nitrogen; PT: Total Phosphorus; GI: Germination Index; EC: Electrical Conductivity. ND: No Data, T: Treatment; TSC: Two-Stage composting, CC: Conventional Composting.Source:(4,13,14,16,19) …”