Carbonization of Municipal Sewage Sludge: A Win-Win-Win Opportunity?.

Disposal of municipal sewage sludge has posed an environmental hazard with negative effects on soil, air, and water quality for many decades. Advanced carbonization technologies can now efficiently convert sludge materials into stabilized charcoals that may be added to agricultural soils to alleviate potential land pollution and enhance C sequestration, soil fertility and crop productivity.

We have completed a series of three greenhouse trials testing the effects of both the CC and SS biochars on the growth of corn seedlings. By growing three cycles of corn plants in succession in the same biochar-amended soil, we were able to investigate biochar effects on soil properties and plant growth as a function of time. In the SS biochar trial, the general trend over all three crop cycles was that both the treated and untreated biochars together with fertilizer improved plant growth over and above fertilizer or biochar alone. In the first crop, untreated biochar alone performed as well as fertilizer, but the positive effect disappeared in the 2^nd and 3^rd crops, where biochar alone performed no differently than the control. The largest effects were seen in the 1^st and 3^rd crops, where both treated and untreated SS biochar together with fertilizer improved biomass production by more than 200 percent.