Foreword

Albert Einstein observed that ‘scientists investigate that which already is; engineers create that which has never been.’ The history of waste to energy (WTE) is a long story of learning, experimenting and evolution. The chapters in this book tell this story from many different points of view. Engineers have been working on the recovery of the energy in wastes from the time that steam engines for power and electric generation were first in operation in the late 1800s. The first ‘destructor’ in England, built in Manchester in 1876, was reported to be operating 30 years later.¹

Joseph G. Branch, the chairman of the American Society of Mechanical Engineers (ASME), self-published a comprehensive book on the subject of 'waste to energy' in 1906.² In this he tabulated the waste generated at the time, and over 100 British and foreign municipal incinerators using typically over 30 tons per day waste for lighting and power uses. He described the power plant built under the new Williamsburg Bridge, to burn New York City waste. At that time waste was carried by horse-carts mostly to be dumped in the rivers. Some carts burned the trash on the way!

After 1906, only a few public WTE plants were built. As internal combustion engines replaced the horses, trucks that were used to haul the waste to landfill or to dump it in the river; much of land areas of Manhattan and other boroughs were expanded by filling with the high-ash-containing trash. After about 1950, as land became more expensive, and population blossomed, local governments began to hire engineers to build refractory chambers to burn the waste, and even wash down the smoke somewhat.

A group of ASME members, as the Incinerator Division, published standards for refractory incinerators to destroy infectious medical waste in 1961.³ In 1966 the ASME Incinerator Committee was formed 'to bring together the foremost authorities in the field of refuse incineration for an exchange of knowledge, experiences and expectations'. This group of engineers was subsequently renamed the Solid Waste Processing Division (SWPD) and is now the Material and Energy Recovery Division of the ASME. The ASME Research Committee on Industrial and Municipal Waste, most recently renamed the ASME Research Committee on Energy Environment and Waste, was organized specifically for research, and to reflect the extension of their activities.

In 1977 the issue of health and environmental effects from human exposure to dioxins suddenly arose. Loosely named here, dioxins are forms of a basic building block in nature, two benzene rings linked together, exhibiting various degrees of toxicity depending upon how many of the six outside points are chlorinated rather than oxygenated. Those with the two outermost joints, number 2,3 and 7,8 chlorinated (2,3,7,8 TCDD) being most toxic to human cells, causing hormonal damage, whereas with all six joints oxygenated, not being toxic.

Formation of dioxins was found in laboratory studies of fly ash from three Dutch plants at temperatures typical of fly ash from combustion of municipal waste, i.e. 450 °F (Olie, 1977). At the same time laboratories were measuring the effects of the dioxins on human health.

By 1977, the US Environmental Protection Agency (USEPA) laboratory in Cincinnati, Ohio, had investigated the temperature and oxygen conditions under which dioxins and other ‘difficult’ chlorinated compounds could be destroyed, i.e. reduced to essentially zero, under laboratory conditions, as gases, not solids.⁴ Dioxins had also become the subject of research throughout Europe. Sweden declared a moratorium on new WTE facilities until a comprehensive research program could be completed.⁵

Particulate (dust) emissions were sampled from the stack of a new trash burning plant in Hempstead, Long Island, New York, by Midwest Research under contract for the newly established USEPA in 1980. Hearing of the dioxin laboratory tests in Europe, David Sussman of the USEPA decided to have the Hempstead samples analyzed for dioxins. Indeed, dioxins were found. The chief engineer of the Hempstead plant immediately brought this report to the attention of a meeting of the ASME Solid Waste Processing Division, stating that 'we will not be allowed to burn municipal waste any more until we solve the problem of dioxin emissions’.

Testing of existing WTE plants worldwide in fact showed an incredibly wide range of dioxins emissions, ranging from 10 000 nanograms per dry standard cubic meter (ng/dscm) (toxic equivalent) dioxin down to 300 ng/dscm, initially with no explanation as to why the range was so wide. A plant in Montreal tested in Canada in 1984 showed results as low as 0.1 ng/dscm, and that is now the international standard.

The ASME Adhoc Committee on Dioxins was immediately organized by Anthony Licata, chair of the SWPD. Arthur D. Little was asked to write a report on all that was known about dioxins, specifically dioxins from combustion of waste, and this report was published in 1980. At that point, no solution to the dioxin problem had been offered.

The first plant to burn shredded municipal waste in a conventional stoker-fired Babcock and Wilcox (B&W) steam boiler was started up in Hamilton, Ontario in 1984. Diagnostic tests were performed to observe the effects of different settings of combustion air dampers, and for the first time dioxins were measured along with CO, oxygen and furnace temperature. Hasselriis analyzed these data and plotted graphs showing the trends of these measurements under the various operating conditions. He presented these graphs at the 1984 Conference of Waste Management in Hofstra, Long Island, and at the Air and Waste Management Conference in Chicago that year. Meanwhile, the Swedish Government had been testing WTE units in Sweden and Denmark, and offered the explanation of nonideal provision of combustion air in the furnace for the presence of dioxins.

Hasselriis' findings needed to be confirmed by full-scale testing of an operating 'mass-burn' WTE plant (the Hamilton boiler was burning shredded RDF (refuse derived fuel)). A plant in Pittsfield, Massachusetts was ideal for comprehensive tests because it had the ability to be operated with flue-gas recirculation, along a full range of furnace temperatures, and excess oxygen levels could be used as part of the broad test program.

The Adhoc Committee on Dioxins obtained support from the New York State Energy Research and Development Authority (NYSERDA) and the USEPA. It was decided to perform comprehensive tests, burning normal garbage and dry paper, and also running tests with added vinyl plastics (as vinyl had been accused of being a major source of dioxins) at the recently started Pittsfield, plant. The most important overall finding was that carbon dioxide and dioxins followed the same trends with furnace temperature and oxygen, regardless of waste composition, moisture or the presence of vinyl in the waste. Hence CO was a good surrogate for dioxins: and continuous monitoring of CO became mandatory for operation of waste combustion. The results of the Pittsfield tests were published at a World Health Organization Conference in Copenhagen in 1987.⁶

Actually, it took another ten years to develop an understanding of why there was such an enormous range in dioxin emissions measured in stacks of different plants. The practice of injecting activated carbon into the flue gases prior to capturing the particulate in a fabric filter became a principal means of controlling the dioxins, in addition to optimizing combustion conditions. Environment Canada⁷ had carried out extensive testing of emission controls on a pilot spray dry/bag-house on an existing WTE plant that showed that such a relatively simple system could reduce emissions to acceptable levels. The scrubber/bag-house system became the standard for plants in the US and Canada.

After the Clean Air Act was passed in 1976, the USEPA first tested all measurable stack emissions, and the health and environmental risks were evaluated. The first tests had been performed in an incinerator in Boston, and included testing for all organic pollutants that it was possible to detect; this was later weeded down to those pollutants that are of significance to health and the environment, especially sulfur dioxide and particulate matter.

The EPA continued to test each plant as a permit condition, collecting a database that could be used to make estimates of emissions from future plants as they were built. Standard deviations of the data were calculated, from which it could be stated, for instance, that 99% of future test readings would be lower than that number.

Credit is due to the US Congress, which became an active supporter of WTE. Congress passed laws that required the utilities to pay 6 cents per kilowatt-hour for electricity for the period of time covered by the bond issue. This launched the WTE industry in the US. By the time this regulation expired in 1990, well over 50 new WTE plants had been built and brought under operation in the US.

The major boiler manufacturing companies of today, such as Babcock and Wilcox (B&W), were founded in the coal power and sugar industry well over 100 years ago. B&W is today building a new plant to burn 3000 tons per day of municipal garbage, and other wastes, to produce 80 megawatts of power to serve the community of West Palm Beach, Florida; enough to serve the modern needs of 56 000 homes in collaboration with perhaps the oldest manufacturers of WTE plants in the world, Vølund of Denmark (founded in 1898). Vølund built its first waste-to-power plant in 1978–1980, supplying thermal energy to the central district heating system of Aalborg. Today, this new plant is currently being rebuilt with the most advanced emissions control technology, to meet or exceed emissions conditions that will be the lowest of any renewable energy facility burning municipal waste in the US or elsewhere.

The ultimate control of all pollutants is described by Jurgen Vehlow in the final chapter of this history, describing the perfect controls that would take all consequences of waste reduction into consideration and find a safe resting place for all residues.

The drawback to the ‘perfect system’ is the cost: obviously from an economic point of view, only by compromises can WTE plants be kept at an economical level compared with alternatives, and relative risk to the community throughout the world, for all communities and countries.

The success story of WTE is the product of the community of engineers that kept developing the plants. Working within small and large organizations, writing papers, being involved in conferences, as parts of academic organizations, visiting plants, reading reports and papers, attending meetings of the Waste to Energy Research and Technology Council (WTERT), SWPD, etc.

This book should be of great interest to, and serve as an exceptional resource for, libraries, students, teachers, plant operators, engineers, managers, environmentalists and the general public. It chronicles the process by which engineers have systematically solved the problems of managing society's wastes and safely converting the wastes into energy, while at the same time recovering materials where practical.