Owing to popular demand among the readership of this blog, I’ve taken a closer look at the original article claiming that spent coffee grounds can be employed as a source of fuel. There are several important details that come though in the paper coming out in the next issue of the Journal of Agricultural and Food Chemistry that have not come through in the press reports.

The press reports suggest that about 340 million gallons of biodiesel can be generated using this method, which I am assuming works (or at least, I declare that I cannot tell you if their method works!). Almost nowhere is the time period over which this 340 million gallons of biodiesel would be produced mentioned in press reports or in the article, but from reading the article one gets the impression that the authors mean per year. However, that number has no support in paper itself.

Rather, there is a different, lower but more impressive number used in the paper. This is the number 2.9 million gallons per year produced by tapping only into the output of Starbucks within the United States. Worldwide Starbucks production .. taking all the used grounds from all the Starbucks in the world … would produce over 4 million gallons per year.

Total biodiesel production per year using all coffee available is estimated (the basis of the estimate not provided in any detail) to be 208 million gallons per year.

An even more interesting way of putting it is this: According to the paper, a business venture using only Starbucks coffee grounds to produce the biodiesel would yield a profit (net) of just over 8 million dollars. Now, that is based on a a fuel cost (wholesale? retail?) of $4.50 per gallon. This may or may not be realistic for a business that gets underway, say, two years from now. The total value of the worldwide industry would be a half billion dollars per year. I any event, it would seem a logical step for Starbucks to make the investment and add the production of a small amount of biodiesel to their line. Admittedly, this is not a Venti amount of fuel, not even Grande, but even a short contribution is a contribution.

It has been noted by commenters and emailers that the total production from coffee would be minimal compared to the overall demand for diesel. This, however, is not important. If we develop a hundred techniques that each operate well on a small scale and each produce one percent of need, then it does not matter that any one technique is insufficient. In fact, having a plethora of techniques has its advantages. One could cite economies of scale as a reason for monolithic approaches to production, but economies of scale are much overrated … at large scales. Such economies kick in early and peter out quickly. One could apply the same logic to individual oil wells: Since a single oil well produces only a tiny fraction of the total need, why bother? Well, because one can drill thousands of wells. And every time you add an oil well to your production, you save money on a per well basis, until some point where you are still producing a small percentage of demand. One continues to gain as one scales up because of risk reduction effects, but that also peters out and eventually is replaced by all the downsides of corporate bigness.

Presumably, one can convert dozens of good sources into biodiesel, and biodiesel can be one of many fuels. o

Compared to other sources of biodiesel, coffee grounds has a number of advantages. One is that production does not smell as bad. In fact, I would assume that production smells good, though the authors do not explicitly state this so don’t count on it. They do explicitly state that compared to using pig fat, this is better with respect to smell. This reduces cost and increases viability because those pesky quality of life regulations require that companies not build smelly biodiesel or ethanol plants just anywhere. There are other ways, chemically, in which the oil extracted from the coffee grounds is better than other sources of oil.

And, getting back to the issue of quantities of production, the data supplied in this paper indicates that a large scale production from coffee grounds would be in the same approximate order of magnitude of production from other sources such as chicken fat. Also, coffee based biodiesel is also more stable than some other biodiesel sources.

Finally, there are outputs from the process that can be fed into ethanol production or used as fuel pellets.

The bad news is not mentioned anywhere: If you can make biodiesel out of coffee grounds, than certainly you can make it out of the coffee before making the beverage. Indeed, you’d get a lot more fuel if you skipped the part about making the Cappuccino or Latte. The employment of coffee as a fuel may be too expensive right now, but if fuel prices ever rose sufficiently in relation to over the counter beverage prices, or if a major controlling agency simply co-opted the coffee for fuel, it is conceivable that there would be a coffee shortage (for drinking coffee) because its use in cars and trucks would be muscling out beverage related application.

If that happens, civilization will end shortly thereafter. So let’s not do that, OK?

Kondamudi, NarasimharaoMohapatra, Susanta, Misra, Mano (2008). Spent Coffee Grounds as a Versatile Source of Green Energy Agicultural and Food Chemistry