Cardbox rejects as feedstock for biochar production is a viable and environmentally friendly option.

The carbon content of cardboard is relatively low compared to some other biomass sources. As a result, the carbon content of the biochar produced from cardboard may also be lower. Higher carbon content in biochar generally contributes to its ability to sequester carbon and improve soil fertility. The higher heating value makes up for the lower carbon content. 

The Oaktree mixes the rejects with Brown fiber in pellets to optimize the process.