Dear List readers, Orange peels have troubled biomethanation processes for long. We have tried orange peels (mix of orange and sweet lime, dominant is sweet lime) both in a solid state fermenter and plug-flow type fermenters where these are fed on an as-is-received basis with no pretreatment.
Fermenting them as a single feedstock brings about some form of inhibition to the overall methanogenic process and the biogas produced even smells of oranges. The inhibition is not to methanogenesis alone but to the overall process as intermediate VFA do not accumulate to toxic levels (c.250-1000 mg acetate equivalent /L). When fed as a part of overall fruit wastes (<20% of total weight), these two do not inhibit the overall process and gas production remains sufficiently high. However, when these fruit peels are dried and powdered and tested for BMP at 0.25% TS, gas production does not seem to be inhibited. Our suspicion therefore is that the essential oils that accompany the peel is the culprit and subjecting these to a steam distillation step prior to digestion could recover the essential oils as a saleable commodity, rendering the peels more digestible. Some of my old friends use a fungal pectinase and a pectinase generating fungus (CFTRI, Mysore) to liquefy these pectin bearing peels and then subjected them to digestion in (the pulpy material remaining after fungal /pectinase treatment) conventional floating drum Indian digesters with much success. I guess I have captured some of the South Indian experience in this field. best regards chanakya -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _______________________________________________ Digestion mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org for more information about digestion, see Beginner's Guide to Biogas http://www.adelaide.edu.au/biogas/ and the Biogas Wiki http://biogas.wikispaces.com/
