In much of west Texas, the iconic Prickly Pear cactus — with its plum-like fruit and forbidding spiked pads — is at best considered a nuisance, and at worst a downright hazard to livestock. But in most of the rest of the semi-arid world — from Mexico and Chile, large swaths of India and South Africa, as well as Spain and Morocco — Opuntia ficus-indica (Prickly Pear) is used in dye-making, as feed for livestock, and, little by little, as feedstock for anaerobic biogas production.
http://www.renewableenergyworld.com/rea/news/article/2014/01/prickly-pear-cactus-nuisance-or-bioenergy-opportunity?cmpid=WNL-Wednesday-January15-2014