Moving forward organics management is likely to come under increasing scrutiny for a number of reasons including cost, climate impact, broader environmental impacts (e.g. phosphorus and toxin leaching) and optimization of renewable energy generation. These are all likely to vary widely due to national regulations, availability and national support for different types of management practices as well as climate goals and aspirations. Having a framework for comparing these options and implications should help those managing different organic materials to assess and communicate them to various stakeholder groups.
Sludge for example, is currently still land-applied in some locales those this is becoming more regulated due to PFAS and other emerging contaminants of concerns. Maine was the first US state to ban land application of sludge. For wastewater treatment plants (WWTP), this is a relatively low-cost option which includes transportation and, in some places, (e.g. Denmark) payment to farmers to apply it to their fields. We are learning that not only does this generate methane but also can render agricultural soils used to grow food to be worthless as the produce is contaminated. Another option is landfilling, which also involves transportation and tipping fees but no infrastructure for the WWTP. In some areas, contaminated sludge or biosolids may no longer be accepted or will come with higher tipping fees. A third option is to digest the sludge to generate renewable natural gas, but this still leaves significant amounts of fiber (digestate) and toxins to be handled. Composting has been another management technique for sludge (or biosolids) but also off-gasses methane and does not mitigate contaminants. Compare these management options to carbonizing sludge which requires significant infrastructure but can reduce methane and contaminants while also generating renewable energy. This option requires less time and land than other options as well.
Each type of organic material is managed differently but carbonization quite often provides a broader portfolio of benefits than current management practices. Developing a deeper, customized version of this framework for existing organics management scenarios could be helpful in persuading local operators to consider shifting to carbonization when existing infrastructure needs to be replaced or when other goals of improving environmental and climate impacts of organics management are prioritized.
