The Cumulative Benefits of Biochar in Agriculture

Sammanfattning: Stockholm Exergi provide district heating in Stockholm and plan to integrate their district heating system with the production of biochar, by building a plant that produces 100MW district heating and 100 000 tonnes biochar per year, in order to reduce greenhouse gas emissions. Biochar may mitigate climate change, but the added benefits of biochar, beyond the benefits of carbon sequestration, lack quantification. This report aims to review, quantify and document the cumulative benefits, with respect to climate, health, and resource consumption, of biochar application to Swedish agriculture, as a livestock feed additive. A life cycle of biochar as a livestock feed additive is illustrated, where the biochar is ingested by livestock and retrieved in manure. The manure is thereafter co-composted with the biochar, and finally, returned to soil. Each step proceeding the initial application carries important benefits to climate, health or resource consumption. Providing all livestock in Sweden with biochar requires 100 000 tonnes per year and may potentially reduce greenhouse gas emissions from livestock by up to 450 000 tonnes of carbon dioxide equivalents (CO2-e) per year. Distributing the biochar to farms across Sweden results in around 10 000 tonnes of CO2-e emissions per year. Hence, the potential net annual reduction in greenhouse gas emissions is approximately 440 000 tonnes of CO2-e in Sweden. This is equivalent to -590g CO2-e/kWh for a biochar plant that produces 100MW district heating. Research also suggests a reduction in greenhouse gas emissions from biochar co-composting and biochar soil application. However, the concentration of biochar retained in manure subsequent to feeding is too low to draw a conclusion regarding its effect on emissions. Health benefits of biochar as a livestock feed additive include reduced (or even eliminated) need for antibiotics, fewer cases of illness amongst livestock, fewer deaths, and higher quality cow milk. The biochar also eliminates manure odour, improving work environment for farmers. Biochar co-composting may reduce ammonia emissions and improves nutrient retention. Applying the co-compost to soils eliminates soil pathogens, detoxifies allelochemicals, increases the growth rate of beneficial microbes, and reduces fertilizer need. Crops will thus become more resistant to mould and biotic stresses.