Volatile fatty acids production from waste rich in carbohydrates: Optimization of dark fermentation of pasta by products

Pasta is one of the most appreciated Italian products around the world. The 31% of the global production of pasta is made by Italian companies: here, about 120 companies assure an annual production of 5.3 million tons of pasta. The pasta not compliant with the required selling standards (for example size, weight) is usually crushed, grounded to power, and used for animals feeding. This study offered a more advantageous alternative for the valorization of pasta by-products, whose mono-fermentation for Volatile Fatty Acids (VFAs) production was not investigated before. In particular, we considered pasta residues to optimize the operational parameters both in batch and in continuous conditions. The first round consisted in batch tests at different Total Solids (TS) con- centration (1.5–10% TS w/w). The 2% TS w/w emerged as the best one, able to assure a VFAs yield close to the 80%. Consequently, this concentration was chosen for the conduction of continuous tests dedicated to the optimization of the best HRT and SRT for the process. The HRT of 3 d and a SRT of 4.4 d allowed the best process performances with a VFAs productivity of 3.48 gVFAs_COD per L of reactor and per day. The optimization of the process conditions for VFAs production led to a greater concentration of butyric acids (about 10% w/w) instead of the mere acetic acid production. Because of the economic value of butyric acid, this result is of particular interest