Denver Zoo Halts Biomass Project

September 29, 2015 By Carl Weinschenk

shutterstock_139962232The Denver Zoo has backed off a plan to turn animal waste into fuel pellets, though it has left the door open to revisiting the idea.

The Denver Post says that zoo officials made the decisions due to financial pressures and technical uncertainty. The plan had been opposed by some area residents who were uncertain about the safety of the project and didn’t like the idea of the placement of what they called an incinerator in the middle of the zoo. To date, the zoo had spent $3.7 million on the project. Officials did not say how much more would have been required to complete the system.

The idea was to use a gasifier to turn dung, wood, plastics and other waste into pellets that could power generators and produce electricity and heat, the story said. If successful, the process would eliminate hauling of 1.5 million pounds of waste annually to landfills, reduce electricity use by 20 percent and cut $8,000 in trucking fees.

There are working gasification facilities, of course. Cogeneration & On-Site Power Production takes a close look at one. The site recently featured a visit to Vaskiludon Voima, which was converted from a coal-fired power and district heating plant to a biomass facility between 2011 and 2013.

3 comments on “Denver Zoo Halts Biomass Project

  1. Total gasification of solid waste creates a synthetic methane gas or Synthesis Gas [CO & H2]. If ‘fuel pellets’ were to be the final product of waste Gasification at the Denver Zoo, then this Gasification System wasn’t doing its intended job at all.

    Incomplete gasification is called Torrefaction or next higher up the Gasification chain is Pyrolysis which produces a ‘carbon black’ substance in addition to the synthesis gas. Total Gasification is NOT achieved with these two other mechanisms. And this mechanical science is very confusing to most people.

    Today, Gasification Technology is making a resurgence. It was originally invented in the late 1800’s and the syngas produced from gasifying coal was termed “Town Gas.” The first gas piped to dwellings and businesses to generate Light, Heat and Hot Water was indeed synthetic methane or synthesis gas.

    Methane NatGas is the simplest carbon molecule being CH4. Losing two hydrogen ions and gaining a large Oxygen atom (as in CO – H2 syngas) allows this simple gas to combust even cleaner. The Oxygen atom contained in syngas doesn’t contain any BTU’s – yet it fans the flames getting all of the carbon components to fully combust.

    The Denver Zoo and nearby neighbors shouldn’t fear Gasification at all. Yet realize that a synthetic methane is what is produced from the animal manure, other solid wastes such as garbage, plastics, wood chips – even ground tires or coal. Yet in total Gasification, there are not “fuel pellets” being produced. The most typical element being produced with Gasification is to cleanly combust the syngas, boil water into steam and produce co-gen steam electricity.

    Yet this co-gen electric isn’t the greatest ‘value add’ from gasification of solid wastes. The greatest value add is to catalytically convent the atoms of C, O and H into liquid fuels. And then, one can make the choice of producing Hitler-version Synthetic Oils (clean burning but all oils still float on water bodies) or water soluble, oil soluble, coal soluble Fuel Alcohols instead.

    There is one type of Rotary Kiln Gasifier without a smokestack. It is so clean in the conversion of solid waste products into mid-stream synthesis gas that this function is performed without a smokestack. No air emissions. No air quality permits are needed. Perhaps something like this would be more appropriate for the Denver Zoo?

  2. Mr Dell,
    You are correct that producing fuel pellets is not the end result of the gasification process, however it is an important step in preparing the fuel for gasification. The process to make the fuel pellets shreds and mixes the waste and then removes the moisture making the waste more efficient to gasify. One company, MSW of Acton, MA, has integrated the process into one device that takes in waste on one end and produces heat, ash and electricity on the other. http://www.mswpower.com/bwec.html
    Fuel pellet production is a step in the process, which may be the same case as the proposed Denver Zoo gasification project.

  3. The concept is a good one, most community concerns would be eased if they saw what a well designed system actually looks like and how it performs. A unit for the Zoo’s stated requirement would come fitted in a 20′ shipping container. It would cleanly convert the zoo poo to around 100 tonnes/year of biochar which would retail out at the gate for visitors gardens for $500/ton. So not just a saving on avoided transport costs. The gas coming off has no horrible emissions after being used in boilers or engines. It could be used to run hot water for heating or at this scale run about a 200kW genset. I would be excited to be involved in a project like this.

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