Waste to Energy: It’s Complicated

Here’s a video on a waste to energy plant in Africa that readers may enjoy.  W2E, as it’s sometimes called, is a complicated subject, due to a number of factors:

Cleanliness of the technology is a relative matter

Anybody can combust municipal solid waste, extract some portion of its chemical energy and turn it into electricity. Before the developed world became aware of the environmental mess we were making ca. 1960, this was the predominant mode of disposing of MSW. However, the waste from this process, both the ash and the gaseous exhaust, is toxic, more or less so depending on the exact composition of the incoming stream.

Other more modern processes, e.g., gasification (use of high temperatures and pressures to effect chemical change without the introduction of oxygen), hold great promise, but most are too expensive for the processing of most forms of solid waste.  That said, the destruction of certain types of medical waste merit the total chemical transformation that plasma arc (high-energy) gasification provides, as do certain other common waste streams.  The combustion of creosote-soaked railroad ties, e.g., releases dioxins, which are some of the most highly toxic chemicals known to man.

Technology Readiness and Reliability

Most of the business plans submitted for review here at 2GreenEnergy contain exaggerations.  In the real world, there are no technologies that are “omnivorous,” or “feedstock agnostic,” meaning that they work equally well with any incoming waste stream.  Similarly, there is no machinery that runs perfectly for indefinite periods of time without cleaning or other forms of maintenance.

Land Use and Other Hazards Associated with Land Fills

These people in Ethiopia mentioned above seem to think that burning their MSW is a fairly clean process, and they say that what’re their doing is the equivalent of planting a large number of trees.  Although that’s almost definitely incorrect, there are real societal benefits that they’re reaping.  The 1400 tons of MSW per day had formed a mountain in the country’s capital Addis Ababa the area of 36 soccer fields and hundreds of feet high, which had become the site of numerous tragic deaths, as the desperately poor picked their way through it in a search to find items of value that could be sold.

In other cases around the world, odor is a significant issue, warranting the use of anaerobic digestion to convert animal waste, for instance, into some combination of fuel and fertilizer.

The take-away here is that one size does not fit all.  There are hundreds of different W2E scenarios, each of which needs to be considered for its unique characteristics.