Anaerobic co-digestion of Euphorbia tirucalli with pig blood for volatile fatty acid production

Abstract

Acidogenic fermentation of biomass to produce volatile fatty acids provides a renewable pathway to industrial chemicals ordinarily derived from petrochemicals. Crassulacean acid metabolism plants such as Euphorbia tirucalli are cultivable on marginal land and offer promising feedstocks for this purpose. This study investigated how the refining of E. tirucalli biomass to fatty acids could be augmented with a high-protein co-substrate, pig blood. Blood mono-digestions provided the highest titres of total fatty acid (up to 38 ± 2 g/L), while at high substrate concentrations, acetic acid was maximal in co-digestions. 75 % blood with 25 % E. tirucalli produced acetic acid titres 40.8 % (p < 0.001) and 30.8 % (p = 0.001) higher than those in mono-digestions of E. tirucalli and blood, respectively. Where acetate is the desired product, inclusion of blood as a co-substrate offers significant benefit for Euphorbia biorefining.