by Emil Morhardt
Disposal of waste animal carcasses is expensive, a nuisance, and more trouble than its worth, at least some of the time in China. Consider that in 2013 over 16,000 dead pigs were dumped into one of Shanghai’s primary drinking water sources (Zhang and Ji, 2024). If this waste product were more valuable, than nothing of the sort would happen. According to these authors the carcasses are, in fact, worth $56/tonne, when converted to biofuel. To prove their point, they used pig carcasses to make biodiesel and biogas. They cooked them in water in an autoclave (basically a pressure cooker) for six hours then extracted the pig fat from the water and converted it to biodiesel. The remaining water was inoculated with anaerobic bacteria from a pig farm digester, and allowed to form biogas, in this case 63% methanol.
The economic analysis assumed availability of a million pig carcasses per year from Zhejiang Province in China. (The province produces 32.7 million pigs a year, with an estimated unintentional mortality of 3%.) Although not formally included in the economic analysis, the authors figure that what remains of the degreased carcasses could be used as fertilizer and some [unspecified] type of industrial raw materials.
Making such a scheme operable is going to take some doing, since the government is going to have to make sure that individual farmers don’t just dump dead pigs into the nearest river, which seems to be a standard approach.
Zhang, Z., Ji, J., 2014. Waste pig carcass as a renewable resource for the production of biofuels. ACS Sustainable Chemistry & Engineering. DOI: 10.1021/sc500591m
