MRBT ‘better’ than EfW for waste disposal

Picture taken from 'What is the best disposal option for the ‘Leftovers’ on the way to Zero Waste?' report.

A new study has found that the most ‘environmentally sound’ disposal option for residual waste is materials recovery, biological treatment (MRBT).

Commissioned by American recycling reprocessor Eco-Cycle, ‘What is the best disposal option for the ‘Leftovers’ on the way to Zero Waste?’ states that the MRBT process is ‘more effective’ than both mass-burn waste-to-energy and landfill gas-to-energy processes.

The aim of the study was to determine ‘the best method for managing out residual waste in order to reduce the harm and risks to public health and our environment’.

The report was an international effort authored by Dr. Jeffrey Morris of Sound Resource Management Group, Dr Enzo Favoino of Scuola Agraria del Parco di Monza, Eric Lombardi of Eco-Cycle, and Kate Bailey, also of Eco Cycle.

Key Findings

The study ran residual waste from Seattle, Washington through five different residual management scenarios: landfill with landfill-to-gas-energy with two different assumptions for gas collection efficiences; energy from waste followed by landfilling and MRBT followed by landfilling (MRBT-to-landfill).

Using a tool developed by Morris, the Measuring Environmental Benefits Calculator (MEBCalc), the study accessed each scenario across seven environmental categories including climate change, water pollution, air pollution and human health impacts.

Reportedly, the MRBT system was shown to be the best choice because it recovered the greatest amount of additional recyclables, stabilised the organic fraction of the residuals, reduced the amount of material to be disposed of in landfill, and minimised the negative environmental and public health impacts.

According to the report, when utilised in a community alongside ‘successful recycling and composting programmes’, MRBT can help support high levels of landfill diversion.

The study modeled an 87 per cent diversion rate for Seattle, based on 71 per cent diversion from current source-separated recycling efforts, with an additional 16 per cent from the MRBT process.

This includes increased recovery of recyclables and the weight reduction of the organic materials from moisture evaporation and biogenic carbon conversion to carbon dioxide.

Other key findings of the report included:

• all of the options resulted in increased pollution;
• the two MRBT-to-landfill scenarios had the lowest environmental impacts across five of the seven categories;
• the climate impacts of landfill depended on the effectiveness of the landfill gas capture system; and
• the combustion of waste for energy had higher relative human health impacts.

The report emphasises that source separation for recycling and composting is still the best environmental option for managing all discards and should be the focus of community efforts.

However, it also stresses the need to reduce the negative impacts of disposal and minimise the need to invest in new disposal facilities.

MRBT Facilities

The flexibility of the MRBT system is emphasised in the report, as it is said to ‘allow for the processing of clean or dirty material streams as a community’s need for change’. This is compared to the energy-from-waste system, which is said to be ‘designed and built for a never-decreasing amount of leftovers’.

According to the report, the MRBT also requires ‘a markedly short time to be designed, built and put into operation’, compared to new energy-from-waste or landfill facilities. It is suggested that this translates into a faster reduction in the negative environmental impacts of waste disposal.

Additionally, the report states that the MRBT is ‘scalable’ and can be designed to serve much smaller waste management districts, allowing a community to treat and manage leftovers locally and thus be more self reliant.

It is also suggested that MRBT facilities can facilitate further materials recovery in the future if paired with a research component to understand the composition of the remaining dry residuals and evaluate strategies to target additional recovery of these items.

“Europe has over-invested in waste incineration”

On the findings of the new study, Joan Marc Simon, Founder of Zero Waste Europe, said: “This report is exactly what we need at the right time to help guide the debate on what to do with residuals once we reach high separate collection rates. Europe has over-invested in waste incineration and needs solutions that deliver environmental safety while still focusing on increasing recycling and reducing material consumption.”

Indeed, the Global Alliance for Incinerator Alternatives (GAIA) has warned that some EU states, including the UK, have the capacity to burn ‘more than the non-recyclable waste generated’. 

This study comes amidst growing concern about residual waste treatment overcapacity in the UK, specifically of the mass-burn. In June, Defra withdrew £217.1 million of PFI funding for three incinerators, including the Merseyside Waste and Recycling Authority’s project, saying: “We now expect to have sufficient infrastructure in England to enable the UK to meet the EU target of reducing waste sent to landfill.”

Further, a 2012 report by waste management consultancy Eunomia claimed the UK could see ‘overcapacity of 6.9 million tonnes per annum’ by 2015/16.

Read ‘What is the best disposal option for the ‘Leftovers’ on the way to Zero Waste?’