Kenya's Waste-to-Energy Community Cooker

An exchange between Global WTERT Council (GWC) associates Perinaz Bhada and Professor Nickolas Themelis about the the community cooker fired by solid waste operating in Laini Saba slum in Kibera, Nairobi, Kenya.

Perinaz Bhada: This community cooker in Nairobi's slum uses garbage as fuel.  Apparently, it achieves temperatures up to 850C by dripping sump oil and water onto a super-heated plate.  This eliminiates the toxins from burning the garbage.  What do you think?  Is it possible to eliminate most toxins in this way on such a small scale?  And if so, can this idea be replicated?  If the toxins can really be removed using this method, then this could potentially be a good way for getting rid of garbage in many slum areas, protecting the environment from reduced open burning, reducing the use of firewood, and providing a source of heat for cooking, heating water, etc.

I look forward to hearing your thoughts on this.

Laini Saba slum, Kibera, Nairobi, Kenya's community cooker fueled by solid waste. A waste-to-energy success.

Prof. Themelis: Dioxins and furans are formed from combustion of materials that contains some chlorine. Food wastes, green wastes and even wood contain a small amount of chlorine, PVC contains about 40% of chlorine.  Burning oil will sustain the fire but even if 850 degrees C temperature is achieved, there will still be dioxin/furans at an estimated concentration of about 100 ng TEQ/standard cubic meter (same as incinerators produced before MACT* APC**). However, the amount of flue gas from such furnaces will be small and all residential wood furnaces produce dioxins/furans but we still use them because the chimney conveys out of range of the occupants. If these African stoves are equipped with proper enclosures and chimneys that lead the furnace gas above the building where the furnace is located, they should be all right.

* MACT: Maximum Achievable Control Technology
** APC: Air Pollution Control

History of Gasification of Municipal Solid Waste through the eyes of Mr. Hakan Rylander

This is an excerpt from Let's speak about Waste To Energy..., an interview conducted by Antonis Mavropoulos and published on his Global View of Waste Management Blog****

Mr. Hakan Rylander, CEO Sysav Company Group

Mr. Hakan Rylander is a former President of International Solid Waste Association (ISWA)  and the current CEO of the SYSAV Company Group. He is one of the most experienced WtE engineers I know, involved in all different phases and aspects of a WtE facility. SYSAV is a role model company in WtE.  Mr. Hakan has held many other key-positions e.g. Chairman of the ISWA WtE Working Group, Swedish Representative in the Nordic Association of Waste Management, Chairman of the Scania Society of Engineers. Currently Hakan is also running the R&D Committee of Avfall Sverige.

Antonis Mavropoulos: What can we expect from the (Waste-to-Energy, WTE) technology in terms of improvements?

Hakan Rylander: - to reduce and minimize the amount of bottom ash. (More here)
- to develop a safe and environmentally correct way of final handling of the flue gas cleaning residues and to recover as much as technical and economically possible of the metal content in these residues and in the bottom ash (More here)
- to increase the electrical efficiency in the waste-to-energy plants. (More here)

About the History of Developing Gasification Technology for Municipal Solid Waste (MSW)

Last but not least, in a recent discussion I heard, probably for the 100th time in last two years, that incineration is dead and that gasification and plasma pyrolysis will soon substitute all incineration plants. What is the current status of those technologies? Are they applicable for Mixed MSW? Are there commercial applications and operational experiences? After all,  is it something we can trust?

Antonis: A lot of people say they are promising and they are more environmental friendly than incineration...?

Hakan: Well,

Media question about New York City's Waste-to-Energy RFP

Prof. Themelis, I'm a reporter at City & State, a New York politics and government newspaper.

I'm writing a short item about New York City's waste-to-energy Request for Proposal (RFP). Marco Castaldi, a professor at Columbia University and an expert on waste-to-energy technologies, told me that the city is moving in the right direction with this, but that older combustion technology should be considered along with newer technologies, such as gasification. I'm told the two main types of waste-to-energy technologies are combustion, which has been used for about 30 years, and gasification, which has emerged over the past five years or so.

He said that he's not for one type of technology or the other, but that as an engineer, it's best to have both options on the table to find the best possible solution for the city. For example, the newer gasification technologies are more versatile, since the gas created can be used in more ways, but it also is more expensive.

Do you agree with this? Is there a risk the city could end up promoting gasification when combustion might be a better option for the city as it tries to divert more waste from landfills?

Response of Prof. Themelis:
I agree with Prof. Castaldi and this is what we recommend to cities and towns who wnat to move away from landfilling: When they issue Requests For Proposals for thermal treatment (WTE) of MSW, they should not close the door to either established or new technologies. ALL technologies, older and newer, must meet very stringent emission standards so the decision of the municipality must be based on economics (lower gate fee to be paid by city per ton of MSW treated). Broadly, these economics depend on three factors: Plant availability (number of 24-hr days per year); energy production per ton of MSW; and capital investment per annual ton of capacity. On this basis, let the most economic process win. Regrettably in less informed/advanced cities, this issue has been so politicized that some RFPs specifically exclude the existing technologies, as was the case in the recent RFP of Mayor Bloomberg, The hope is that newer WTE technologies, such as gasification, will be more acceptable to people who for over twenty years have opposed any form of WTE for NYC; the result is that the City today landfills more wastes than in 2001. The scientific fact is that gasification is partial combustion, to produce syngas, followed by full combustion of the syngas to produce energy. All thermal treatment processes, old, new and future ones, require full combustion. People who prefer landfilling in other states to WTE in their own state are opposed to any type of WTE, as it happened to the Staten Island part of the NYC RFP last week.