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There was an interesting discussion on the Biofuel Group on LinkedIn.com a couple of weeks ago about the efficacy of used coffee grounds as a source for biodiesel. The discussion got started because of the appearance of a news article that claimed that biodiesel could be made from used coffee grounds for $1.00 per gallon. Apparently that is the processing price for extracting the oil from the dried grounds and chemically converting it to biodiesel.

Biodiesel from Instant Coffee Manufacturing

One writer, MK Balaji, quoted from a study reported on Nestle.com about their use of used coffee grounds from their instant coffee production. According to the resulting discussion it is noted that potential 10-15 tons per day of biodiesel production would not offset the loss of fuel value the facility gains by burning the coffee grounds. This is even more true when one considers that the grounds being burned can have a higher moisture content than the grounds going through the oil extraction process so burning of the grounds avoids the added fuel cost of drying the grounds.

It is possible that a grounds drying process could be designed to use the waste heat from the boiler. A well designed coffee oil extraction process might be able to be designed that would take such dried coffee grounds, extract the oil and feed a drier fuel, minus the oil, to the boiler. I would expect that the fuel value of the second stage waste grounds would still be less than the fuel value of the dried grounds minus the fuel value of the biodiesel.

Biodiesel from Coffee Shops

MK Balaji ends his comment by noting that the only other concentrated source of coffee grounds is coffee shops. Individual shops would not have a large enough waste stream to justify an on-site coffee oil extraction process. On the other-hand a relatively low cost waste consolidation effort could be established. For the most part those grounds are now heading to landfills.

Most of the coffee shop chains use a dedicated trucking fleet to deliver supplies to their facilities. Those trucks return to the distribution centers running empty. The addition of containers of wet coffee grounds on the return trip would result in insignificant increase in fuel consumption on that trip.

The cost of sorting and storing pending shipping would not be large. It would be mainly a training effort and developing efficient procedures. No new personnel would be required at the retail level to make this collection process work.

The cost of the fuel produced would certainly not be $1.00/gal because there would be some level of collection cost and the installation of the processing equipment would have to be added to the cost of production. The byproduct stream of dried oil-free grounds could be used as a fixed site fuel or it could be composted and sold as a soil amendment. It could possibly be used as a cellulosic ethanol source. In either case this could help to pay for the production costs.

Ecological vs Economic Action

This is not a major new fuel source and it is certainly not an answer to our fuel dependency issue. Neither would it be a major revenue stream. But, it is something that can contribute in a small way to our current green house gas problem. If a carbon-cap-and-trade process is put into place, this system could become economical depending on how the rules were written.

Learn more about this author, Patrick Coyle.
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