Expert Insight

Integrated Energy from Waste Plants - a One-Stop Solution for Municipalities

Securing a solution to both waste management and renewable energy generation obligation issues has, over recent years, become something of a “holy grail” for municipal and regional authorities worldwide.

This article puts forward an argument in favour of the concept of bespoke, modular integrated plant configurations, capable of delivering to municipality authorities a one-stop solution which complies with the “proximity principle” requirement of treating waste at or near the point of its arising, and delivers the environmental benefits arising from decentralised energy generation.

Within the European Union, Directives requiring ever more stringent levels of compliance with regard to municipal waste (MSW) handling, treatment, and disposal, combined with increasing financial penalty levies for non-compliance, are a major concern for municipalities and, where such services are contracted out, their waste management contractors.

Whilst many “stand alone” MSW treatment processes, ranging from landfill through AD to “plain vanilla” incineration, are commercially available and in operation, few “advanced technology” treatment configurations have yet been developed which meet either the market or - arguably, more importantly - investment/finance sector requirements in respect of being “proven technology” or economic viability.

The writer argues herein that current evaluations of technical risk attached to such plant configuration proposals are, by and large, over-stated and an unnecessary barrier to the implementation of projects. Furthermore, economic viability can be underwritten by combining the “front end” waste treatment element with a “back end” power generation element which, as argued below, should qualify as renewable energy and therefore eligible for “green” tariff treatment.

Importantly, Article 2 of EU Directive 2001/77/EC provides the following definition of renewable energy sources:

(2)(a) - ‘renewable energy sources’ shall mean renewable non-fossil energy sources (wind, solar, geothermal, wave, tidal, hydropower, biomass, landfill gas, sewage treatment plant gas and biogases);

(2)(b) - ‘biomass’ shall mean the biodegradable fraction of products, waste and residues from agriculture (including vegetal and animal substances), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste.

Typically, the front end element of an integrated plant configuration could consist of a waste reception phase, a heat/MBT phase, inert and recyclates separation, and conversion of the residual biomass into RDF (refuse derived fuel) with a biodegradable fraction in excess of 90%.

The generation element could consist of either a boiler and steam turbine configuration (with comparatively low overall electrical efficiency) or, (let’s push the envelope here) a gasification and gas engine configuration delivering comparatively high efficiency, converting the fuel into heat and power. The addition of an ORC (Organic Rankine Cycle) unit could further enhance the plant’s overall efficiencies.

With regard to technology risk perceptions, the writer argues that all of the constituent elements are, individually, based on tried and tested, “proven” technology – heat treatment by means of, for example, autoclaving, has been around for a century or so, materials separation technology for decades, and pelletising likewise. Gasification, for those of us old enough to remember the days before the advent of natural gas, was the basis for generating the “town gas” on which domestic cookers, fires and industrial furnaces ran – a process developed in the 19th century.

There is, admittedly, some validity to the argument that the gasification of waste has yet to be proven on an industrial scale, however the configuration being suggested for discussion here results in the gasification not of waste, but of biomass (as defined under the EU Directive) pellets. The writer is not aware of any current commercially available gasifier technology which is likely to experience problems with biomass pellets as a feed-stock.

The conversion of the residual biomass into RDF can, subject to certain criteria in respect of contaminants and others, result in the fuel product ceasing to be classified as waste under the definitions applied by the EU. Any subsequent use of the fuel would then take the power generation process outwith the provisions of the EU Waste Incineration Directive.

The technology “risk”, appears therefore to be attached not to the underlying technology but to the process interfaces within the configuration, and is one which should be capable of evaluation and acceptance by suitably experienced EPC contractors.

With regard to the economic viability issues, waste treatment/conversion plants generally are able to charge “gate fees” for the reception of waste, and should be able to deliver power to the distribution grid at renewable energy tariffs (with the potential for heat delivery to a district heating grid, if applicable, or to a direct end-user – e.g. schools, leisure centre, industrial/commercial units, etc.). An integrated project will therefore benefit from a dual income stream which, on the assumption that a plant will operate for 8,000 hours per annum, should generate figures capable of satisfying most investment return requirements.

The market for such an integrated plant is, arguably, world-wide although certain authorities have yet to come to grips with the concepts of either paying for waste treatment, or renewable energy tariffs, or both! Nevertheless, a limited number of such projects are currently in development phase, and the results eagerly awaited – as usual, “first to market” will become the benchmark against which other configuration will be measured.

by Chris Moore

See previous articles