Effects of different gasification biochar grain size on greenhouse gases and ammonia emissions in municipal aerated composting processes

Bibliometric analysis of biochar-based organic fertilizers in the past 15 years: Focus on ammonia volatilization and greenhouse gas emissions during composting

Biochar-based organic fertilizer is a new type of ecological fertilizer formulated with organic fertilizers using biochar as the primary conditioning agent, which has received wide attention and application in recent years. This study conducted a comprehensive bibliometric analysis of the main hot spots and research trends in the field of biochar-based organic fertilizer research by collecting indicators (publication year, number, prominent authors, and research institutions) in the Web of Science database. The results showed that the research in biochar-based organic fertilizer has been in a rapid development stage since 2015, with exponential growth in publications number; the main institution with the highest publications number was Northwest Agriculture & Forestry University; the researchers with the highest number of publications was Mukesh Kumar Awasthi; the most publications country is China by Dec 30, 2022. The hot spots of biochar-based organic fertilizer research have been nitrogen utilization, greenhouse gas emission, composting product quality and soil fertility. Biochar reduces ammonia volatilization and greenhouse gas emissions from compost mainly through adsorption. The results showed that adding 10% biochar was an effective measure to achieve co-emission reduction of ammonia and greenhouse gases in composting process. In addition, biochar modification or combination with other additives should be the focus of future research to mitigate ammonia and greenhouse gas emissions from composting processes.

Effects of excess sludge composting process, environmentally persistent free radicals, and microplastics on antibiotics degradation efficiency of aging biochar

Simulation of microbial aging biochar in compost is an important index for evaluating the biochar degradation efficiency of antibiotics. In this study, biochar was prepared by adding microplastics (MPs) to sludge, and the degradation effect of biochar/(peroxymonosulfate, PMS) on antibiotics was evaluated during the compost aging process of biochar. After the compost aging of biochars, the antibiotic degradation efficiency of HPBC500, HPBC500 + polystyrene (PS), HPBC900/PMS, and HPBC900 + PS/PMS decreased by 6.47, 15.2, 10.16, and 10.33 %, respectively. Environmentally persistent free radicals (EPFRs) and defect structure were the main contributors to the activation of PMS. EPFRs produced through PS pyrolysis of biochar exhibited strong reactivity but poor stability during the degradation of antibiotics. Biochar enhanced the growth of microorganisms in compost but reduced its specific surface area. The antibiotic degradation efficiency of the biochar was positively correlated with the concentration of EPFRs. This study elucidated the durability of different biochar toward antibiotic degradation.

Effective Carbon Dioxide Mitigation and Improvement of Compost Nutrients with the Use of Composts' Biochar

Composting is a process that emits environmentally harmful gases: CO2, CO, H2S, and NH3, negatively affecting the quality of mature compost. The addition of biochar to the compost can significantly reduce emissions. For effective CO2 removal, high doses of biochar (up to 20%) are often recommended. Nevertheless, as the production efficiency of biochar is low-up to 90% mass loss-there is a need for research into the effectiveness of lower doses. In this study, laboratory experiments were conducted to observe the gaseous emissions during the first 10 days of composting with biochars obtained from mature composts. Biochars were produced at 550, 600, and 650 °C, and tested with different doses of 0, 3, 6, 9, 12, and 15% per dry matter (d.m.) in composting mixtures, at three incubation temperatures (50, 60, and 70 °C). CO2, CO, H2S, and NH3 emissions were measured daily. The results showed that the biochars effectively mitigate CO2 emissions during the intensive phase of composting. Even 3-6% d.m. of compost biochars can reduce up to 50% of the total measured gas emissions (the best treatment was B650 at 60 °C) and significantly increase the content of macronutrients. This study confirmed that even low doses of compost biochars have the potential for enhancing the composting process and improving the quality of the material quality.