Last week we had the chance to talk with Bill Davis, the President of Ze-gen. This three year old company is possibly the furthest along in the race to develop technology to turn waste into fuel – eliminating the need for landfills in the bargain.
Each year, the United States produces about 100 million tons of construction debris, and about 220 million tons of municipal solid waste. Currently nearly all of this waste goes into landfills.
Pouring the foundation at Ze-gen’s pilot
plant in New Bedford, Massachusetts.
What Ze-gen has done in New Bedford, Massachusetts, is set up a demonstration plant to accept up to ten tons per day of construction and demolition residual material. The material is used as the feed stock in a gasification process that utilizes molton bath technology.
The result of this process, which Davis emphasized is not the same as incineration, are “syngas” (primarily carbon monoxide and hydrogen) which can be used to generate electricity, and slag that can be used for construction aggregate.
The reason the New Bedford location was chosen is because it is next to an existing “transfer station” where construction and demolition waste is shredded prior to transfer to landfills. This shredding process yields a mixture of 90% wood, 5% residual metal, and 5% silica (with small amounts of other material) that looks like bark mulch. Having this materials prep already done allows the feedstock to be more easily tested in the 2,700 degree (fahrenheit) furnace.
Davis said that right now they are perfecting the design of the tubes being used to feed the material into the molton bath. This should take a few more months. After settling on a design to move materials from the shredder to the furnace, the next step will be to go into continuous operation and do gas analysis. As Davis put it, “we are looking at the quality and consistency and BTU level and contaminents that are in the stream. That will inform the engineering for the gas cleanup system.”
When asked about possible difficulties prepping construction debris and municipal solid waste, Davis noted “it appears wastestreams over time are surprisingly consistent,” and “we have some proprietary technology to drive the variability out of the feedstock.”
Developing technology to turn municipal solid waste and construction & demolition residue into electricity and construction aggregate is not easy. Davis estimates it will be sometime around 2010 or 2011 before they will have a full scale facility accepting waste and producing electricity. In order for the capital expense to be justified by the revenues over the lifetime of the plant, not only “tipping fees” (payments to accept and process waste streams – replacing the fees charged by landfill operators) are necessary, but also revenues from sales of electricity.
Evidently the prospect of municipalities all over the USA eventually adopting this technology, however, has attracted top tier investment in Ze-gen from Flagship Ventures and Vantage Point Partners – with the most recent round of financing concluded in the Summer of 2007.
And how much energy could converting 100 million tons of construction and demolition residue along with 220 million tons of municipal solid waste generate per year? Based on the generally accepted 2.11 kilowatt-hours of recoverable net energy per pound of waste, the USA could generate 154,000 megawatt-years of electricity per year, which equates to 4.61 quadrillion BTU’s. With the USA currently consuming around 100 quadrillion BTU’s of energy per year, reprocessing 100% of these waste streams would offset about 5% of the energy currently consumed in the United States, along with eliminating the need for landfills.