15-05: Conversion of MSW into biobutanol

Municipal solid waste (MSW) is a cheap and globally available feedstock which can be converted into chemicals and fuels such as acetone, butanol and ethanol (ABE) following a mild and environmentally friendly pretreatment. The composition of MSW varies depending on its source, but variation can be minimized by the removal of unwanted material (pre-screening). Owing to the presence of processed wood materials, MSW is largely lignin-free, and in many cases also hemicellulose-free, which makes it easier than many other lignocellulosic feedstocks to process. However, sterilization can be challenging. We have shown that ~110 kg ABE can be produced per ton (1000 kg) dry weight (dw) of MSW feedstock. MSW was first thermo-mechanically pretreated, then enzymatically hydrolysed, during which 30-40 % (w/w) of the MSW was converted into fermentable sugars. Commercial cellulases were used for the enzymatic hydrolysis and hemicellulases were shown not to have a significant effect on sugar release. The sugar rich hydrolysate was then supplemented with a suitable microbial culture medium and fermented into ABE using GBL’s proprietary microbes. The initial process produced 87.5 ± 0.7 (n=2) kg ABE per ton (dw) of MSW. Further improvements were made by introducing a pre-sorting step in order to remove unwanted materials from MSW which might otherwise hinder or obstruct the process and by using an improved supplement during fermentation, resulting in production of 110 ± 2 (n=2) kg ABE per ton of the pre-sorted MSW.