Biochar from human waste could solve global fertiliser shortages, study finds | Agriculture

Wood charcoal made from human waste could help solve fertilizer shortages as well as reduce pollution and energy consumption, a study revealed.

Biochar is a form of wood coal made from high -heat treated organic matter, which is often used on agricultural soil as fertilizer. The process also eliminates carbon from the atmosphere, making it a useful carbon well.

The study estimated that biochar based on solid human excrement could provide up to 7% of the phosphorus used worldwide each year. Although the Biochar process only converts solids, nutrients from urine could be added, and researchers have found that this could provide 15% of the annual phosphorus application, 17% nitrogen and up to 25% of potassium.

The treated wastewater sludge is already distributed over agricultural land, but its use is controversial because it often contains microplastics, heavy metals, PFAS forever chemicals, pathogens and pharmaceuticals. Researchers say that biochar can avoid this problem by separating waste from the source.

The study estimated that the biochar process could decrease both the weight and the volume of solid excrement up to 90%, which represents a significant gain in efficiency compared to the transport of purification sludge, due to the high water content of the latter.

The Biochar production process also makes it possible to adjust the proportions of nutrients according to the needs of individual crops. This can solve the problems associated with the use of fertilizers such as the growth of weeds and eutrophication – when excess nutrients lift in groundwater, causing rapid growth of algae which exhaust the availability of oxygen and reduces sunlight available for underwater ecosystems.

Dr. Johannes Lehmann, professor of soil biogeochemistry at Cornell University and principal author of the study published in the journal Pnas, said: “Talking about wastewater is not as glamorous as renewable energies, but the prevention of waste of resources by creating a circular economy is also essential to green transition.”

Agriculture represents 25% of global greenhouse gas emissions, according to the intergovernmental panel on climate change. As demand has increased on world agricultural systems to provide enough food for everyone, the same goes for its appetite for fertilizers to reconstruct the nutrients of the soil.

Synthetic fertilizers provide three main nutrients to soils – nitrogen, potassium and phosphorus – and all three involve production processes with high energy intensity and often destructive. Nitrogen is fixed from air to make ammonia via the HABER process, and by transforming this into nitrogen fertilizers emits approximately 2.6 billion gigatons of CO2 per year – more than global aviation and combined shipping.

The mining of phosphate rock for phosphorus definitively marked natural landscapes and transforming it into fertilizers also leads to radioactive phosphogype as a by-product. Potassium potassium extraction contributes to the salinization of the soil and the contamination of fresh water because of its large quantities of sub-products of waste salt.

According to Lehmann, “the implications [of biochar resource recovery] Go beyond agriculture and involve economy and geopolitics. As finished mineral resources become rarer, countries with no major reserves may become dependent on those with their agricultural needs and their food security. For example, Morocco holds 70% of phosphates from around the world.

“Instead, an alternative future where nutrients are recycled in a circular economy could allow countries to produce food without counting on imported fertilizers, by recalling the problems of environmental justice in the world South by potentially attenuating climate migration, one of the main drivers of which is agricultural insufficiency.”