Paul Connett on Zero Waste

A video of Paul Connett’s talk in Denver on July 30, 2015.


Questions Linger Over Denver Zoo’s Plan to Convert Trash

Written by journalist Josh Schlossberg and published in the Glendale Cherry Creek Chronicle,  “Questions Linger” examines the soundness of the Denver Zoo’s proposed waste to energy plan.

From the article:

The Denver Zoo is more than halfway through the construction of a first-of-its-kind energy facility to be fueled by elephant manure and trash — including plastic and food scraps — that would provide 20 percent of the Zoo’s electricity, and heat its elephant exhibit.

The self-described “greenest Zoo Poo 3 9-15zoo in the country” is framing its plan to convert millions of pounds of annual waste into an alternative fuel source as an environmental leap forward that will help it achieve its goal of Zero Waste by 2025.

Critics, however, including local residents, the Rocky Mountain Chapter of the Sierra Club, the former director of the American Environmental Health Studies Project, and a U.S. Environmental Protection Agency (EPA) scientist, voice concerns ranging from air pollution, undermining of recycling and composting efforts, and environmental justice issues.

The Denver Zoo declined requests by this reporter for a tour, interview, or statement for this article.

Green Light For Green Energy?

The Zoo’s “biomass gasification system” has been 10 years in the making, developed by Zoo staff in partnership with the City and County of Denver, National Renewable Energy Labs, Colorado Department of Public Health and Environment (CDPHE), Colorado School of Mines, and University of Colorado.

The facility, which is 50 to 75 percent installed, according to minutes from a June 3, 2015, Denver Zoological Foundation meeting, is located in the Toyota Elephant Passage Exhibit on the Zoo’s southern boundary, adjacent to Duck Lake in City Park.

The project has undergone technical review by CDPHE and the City Council, received its construction permit, and is awaiting approval for an air permit. The State also issued water quality and sewer use permits, though a wastewater permit will not be granted until the facility is operational and liquid waste can be analyzed for potential contaminants.

Fuel To The Fire

The Denver Zoo gasifier will source its fuel from 750,000 pounds of elephant dung per year, along with 3 million pounds of waste from the zoo and outside sources, including: wood chips, food waste, waste paper, biodegradable plastic, non-biodegradable plastic, aluminum and other metals, according to a June 20, 2013, email exchange between EPA and CDPHE. Denver Zoological Foundation minutes state that fuel will be “87-89% biomass depending on the season.”

The materials will be shredded, dried, and converted into pellets and exposed to high temperatures in a low-oxygen environment to create a combustible synthetic gas (syngas), that will be mixed with natural gas to power generators, supplying 20% of the Zoo’s electricity. The leftover heat will run through pipes to heat the Toyota Elephant Passage Exhibit.

The facility is permitted as a controlled partial combustion system, with some aspects of the technology kept from the public as trade secrets. Trash and biomass gasifiers are still in the experimental stages and “not yet proven in commercial applications,” according to the National Renewable Energy Labs.

While the Zoo has avoided the use of the term incinerator, the EPA-funded Combustion Portal defines an OSWI (OtherOLYMPUS DIGITAL CAMERA Solid Waste Incinerator) as “incinerators that due to their small size or other characteristics are not covered under other incinerator air emissions regulations.” The Zoo’s Engineering Design and Operations Plan (EDOP) states that the Zoo will follow the OSWI requirements, while referring to the “incineration (thermal conversion) of waste material.”

The construction permit issued by CDPHE explains that the facility will utilize a thermal oxidizer — which the EPA refers to as a thermal incinerator — for start up and shut down, where excess gas will be combusted in a flare.

Zoo staff will remove tars that build up in the scrubber and send them through the gasifier. Up to 60,000 pounds of ash per year will be a byproduct of operations, which will be landfilled.

The article continues here and questions the veracity of claims by the Zoo that its efforts reflect zero waste principles.

Posted in DZF

Denver Zoo, Zero Waste Program (Biomass Gasification)

Here’s the description of the gasifier from the Rocky Mountain Chapter, ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) 2015 conference:

Denver Zoo’s Waste to Energy Program will convert 90% of the Zoo’s waste (from trash to animal waste) to clean, sustainable energy by using a biomass gasification system. The process of becoming a zero waste facility by 2025 starts with reducing the waste stream and promoting recycling and ends with converting remaining waste to energy. The biomass gasification project will chemically convert zoo waste in a high temperature, low oxygen process into a usable combustible gas. The resulting energy generated is expected to meet 20% of the zoo’s energy needs while managing the expectations of the owner and design team.

But does the use of the gasifier really reflect zero waste principles?

Vote (of no confidence) for Denver Zoo’s Gasifier

Via youtube, a video circa 2010 illustrating the potential waste stream for the Zoo’s gasifier. Materials – including park trash consisting of what appears to be cholorinated paper products and PLA plastics (which could be composted)  – are shredded, “pelletized,” then utilized to manufacture “syngas” or synthetic gas.

The video doesn’t mention potential pollution to surrounding City Park neighborhoods, any air scheduled monitoring, toxic emissions from the gasifier, and ash that is generated and most likely treated as a hazardous waste. So where are the “energy” savings from cradle to grave? Adhering to true zero waste principles?



INC Approves Resolution on the Incinerator

On August 11, 2015, INC (Inter-Neighborhood Cooperation) passed a resolution on the proposed incinerator at the Denver Zoo. The solution calls for the following:

1.) the Denver Zoo to document relevant, substantive technical and operational details of its OSWI Incinerator and release this information to the public, and

2.) the Denver City Council to conduct a substantive and technical review of the Zoo’s OSWI Incinerator plant through hearings before its designated Infrastructure and Culture Committee, and when necessary, using its full subpoena powers, taking testimony from Denver Zoo Foundation administrators, engineers, scientists, environmental experts including qualified and credible third parties along with representation from environmental justice groups, Registered Neighborhood Organizations and City Park neighbors to determine the safety and health risks posed by the use of the incinerator, before it be allowed to proceed and to operate.

The resolution can be read in its entirety here.

Paul Connett Talk in Denver

Please join us for a unique opportunity to share an evening with one of the world’s foremost experts on incineration and zero waste, Dr. Paul Connett. Dr. Connett will address health and safety concerns of incineration and waste to energy,  as well as discuss the benefits of zero waste.

This topic is timely in view of Denver Zoo’s plans to build and operate an incinerator at the Denver Zoo.

Ford Warren Branch, Denver Public Library
6:00 -8:00 p.m.
Thursday, July 30, 2015
2825 High Street, Denver CO 80205

RSVP here.


Deconstruction of the CD

A  certificate of designation (CD) is

a document issued by the local governing body authorizing the use of land for a solid waste disposal site or facility. The CD is issued if it has been determined that the technical standards set out in regulation are met and after local issues are considered and satisfied. Anyone operating a facility for solid waste disposal where processing, treatment, or final disposal of solid waste is performed must obtain a certificate of designation (6 CCR 1007-2 Section 1.3.3).  Examples of such facilities include municipal solid waste landfills, certain private solid waste landfills, composting facilities, and solid waste incinerators.


The Zoo’s undated Executive Summary – Certificate of Designation Application — Denver Zoo Waste-to-Energy System  (submitted by Denver Zoological Foundation, Inc., as Applicant) is an interesting public document for several reasons.

First, the Denver Zoo describes the “machine” as “part of an innovative waste to energy system.”

Secondly, the Zoo’s CD acknowledges an existing incinerator housed at the Denver International Airport (DIA), permitted by an 8/28/2000 Denver City Council Bill 0652, Ordinance 2000-0696);  the Zoo’s Executive Summary states “the last CD application that was reviewed and approved by Denver City Council was Denver International Airport CD September 5, 2000. Ordinance #696 Council Bill 652.”  By mentioning the DIA incinerator in its Executive Summary, are we to take the Zoo is justifying the use of a polluting technology?

Third, the Zoo’s public outreach process has failed.  We find there is a distinction between between advertising /marketing and public education on pollutants and potential harm to individuals and nature from the “waste to energy system.”  While the Zoo is correct in its CD that it “has been sharing the story of the planned waste to energy system publicly for several years” and probably utilized “used far-reaching communication channels including a member publication reaching $65,000 area,” we pose that if a poll was done of residents who live in the Zoo-City Park vicinity, would they be aware of the Zoo’s plans? How upset conditions (when the flare or gasifier malfunctions) would impact residential neighborhoods?

Furthermore, the Zoo is mistaken about Inter-Neighborhood Cooperation’s (INC) support of the project, including its actions that “formally voted to support the project.” INC did not support the waste to energy project. In fact, on its Web site, INC states “we did not have enough information to make an informed decision.”

Lastly, the CD is interesting for its list of appendices to the Engineering Design and Operations Plan (EDOP). Some of the Appendices are available at the City Council’s site. Some are not. None of the “appendices” are labeled as appendices to the EDOP, making learning about the Zoo’s project increasingly difficult.


Also see draft bill CB 14-0941 dated December 10, 2014 Ordinance granting a certificate of designation for the “waste to energy system,” which is unsigned; the Zoo created a handout (no date) describing the certificate of designation process to the Denver City Council. In this “process” document, the Zoo states the project is  “planned for no effects on nearby surroundings.”