Treatment of natural rubber latex serum waste by co-digestion with macroalgae, Chaetomorpha sp and Ulva intestinalis, for sustainable production of biogas

Biogas production is proposed as an alternative approach to using natural rubber Hevea brasiliensis latex serum, a major waste product from the production of concentrated latex. To Make the most efficient use of the reactor size, the addition of macroalgal biomass as a co-substrate to the fermentation system was investigated. The biogas yield of latex serum as a single substrate was (398 +/- 14) L per kg of volatile solids added (VSA). For the co-digestion system, algae mixed with serum were investigated at wet mass ratios of Chaetomorpha sp. to Erivrt ildesLittalis to serum at 3 : 0 : 1, 2 : : 2, 1 : 0 : 3, 0 : 1 : 3, 0 : 2 : 2 and 0 : 3 1 The co-digestion system with latex serum at 2 to 3 out of 4 parts produced the highest biogas yields within the range of 422-460 L kg(-1) of VSA. Other parameters such as carbon to nitrogen mass ratio, total solids content and initial pi value were investigated at the constant ratio of 1 : 3 of Chaetoniorpha sp to latex serum, and the parameter settings of 15, 10.5 % and 7, respectively, were close to optimal, with all (888 155) L kg(-1) of VSA cumulative gas yield. The methane yield of the optimised system over 45 days was (197 +/- 16) L kg(-1) of VSA and the reduction in COD was (40 +/- 4) %. Latex serum, whether alone or co-digested with algae in biogas production, appears to he promising, for the management of waste in concenrated latex production. (C) 2014 Institute of Chemistry, Slovak Academy of Sciences