Getting More from Your Sludge

Richard M has been pondering efficient modern transport with a green, historical eye. He asks:

If an oil tanker brings crude oil from the Middle East then takes on a backload of British sewage sludge as ballast. Anaerobic digestion produces methane to fuel the engines for the journey back to the desert oil-fields. The ship now has a load of organic material to raise the fertility of the desert to produce food crops.

This is the reverse of Victorian ships collecting guano to fertilise British land. Sewage becomes an exportable asset, not a polluting burden. The ship’s engines run for free for half the mileage. Win,win?


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