Early analysis of waste-related climate change impacts focused on landfill, with less attention given to conventional alternative disposal routes. The benefits of mainstream alternatives, recycling commodity materials, such as paper, and energy recovery from combustion, through offsetting energy and materials from fossil fuel and virgin sources, are now recognised. A separate Defra-funded research project (WR0602) examines policy-related opportunities for the full range of waste streams.
The Landfill Directive requires the diversion of biodegradable municipal wastes, in the UK predominantly those produced by households, from landfill. As a consequence, the future management of these waste streams will change substantially. There is the potential increasingly to divert other biowastes from landfill in order to avert the potential release of methane, a powerful greenhouse gas, to achieve the environmental benefits that also accrue, to avoid the rising costs of landfill and the Landfill Tax, and to capture economies of scale from the co-management of waste streams. In due course there may be an obligation to divert non-municipal biowastes from landfill.
Biological treatment of biowastes, through composting and anaerobic digestion, is conceptually attractive because of the opportunity of securing `closed loop` management through the return of a product to soils. These management routes are often perceived, particularly by the public, as offering overwhelmingly positive environmental benefits, and as being delivered through small scale `local` projects.
However, with respect to their environmental benefits, compost and digestate products differ from commodity materials, where greenhouse gas (GHG) benefit data are readily available. Assessing the benefits of substituting conventional products, such as fertilisers and soil conditioners, is difficult. Functionality, or the service delivered by the products, is also complex and uncertain. For example, the contribution to soil carbon sinks made by applying compost products, and the duration over which carbon is held, or sequestered, is frequently overlooked.
The alternative to biological treatment, and sometimes combined with it, is some form of combustion with energy recovery. However, for biowaste fuels, most technologies are poorly tested in the UK market, with markets for these secondary fuels, the environmental benefits secured by offsetting conventional fuels that release fossil carbon, and the performance of plant, all relatively uncertain.
The overall aim of this research project is to examine, in greater detail than possible under the programme of work currently underway in WRT237, but building directly upon it, the GHG costs and benefits of the use of the secondary products of biowaste treatment. The project will deliver a robust assessment of the scale of benefits resulting from the use of secondary products and fuels under different policy options.
This project examines the potential GHG benefits of biowaste treatment and the substitution of different products and fuels. Data is assembled on likely markets, and the best evidence compiled on the benefits accruing under different policy scenarios and theoretical assumptions (for example for carbon sequestration). Comprehensive sensitivity testing delivers clear and concise information on the relative benefits of biowaste treatments and the scale of benefits that might be secured under different policy options.