Dare you challenge your own beliefs?

Dare you challenge your own beliefs?
27 November 2018

Nik Spencer did, when he asked Ricardo to use Life Cycle Assessment (LCA) to evaluate the credentials of his new “environmentally friendly” technology. At Ricardo, we use scientific best practice to investigate the facts impartially, meaning that sometimes the results are different to our clients’ beliefs. Would that be the case for Nik?

Nik is a serial entrepreneur and, for the last 5 years, has been working on a revolutionary household appliance. The Home Energy Resources Unit (HERU) generates heat for water from everyday items that would otherwise be discarded as waste. The HERU uses pyrolysis via a heat pipe to convert the materials into an oil phase (neutralised with detergent before being sent to sewer), a solid carbon-rich char, which is combusted in situ post pyrolysis, and a gas phase that is scrubbed with water before being combusted in the household boiler. The HERU is designed to operate such that non-combustible materials (notably metals and glass) emerge free from contamination and composites materials that might have previously been attached, making them suitable materials for recycling via bring banks. Otherwise, however, the entire waste collection infrastructure becomes redundant.

Two traditional waste management systems were modelled as alternative approaches to the HERU; collecting co-mingled mixed dry recyclables for sorting at a materials recovery facility, and using a kerbside sort system to separate them ready for onwards transport to reprocessors, in the UK and further afield. Organic materials were assumed to be composted, or anaerobically digested to produce heat and/or power. Residual waste was mostly incinerated with power recovery or simply landfilled.

It can be seen from the above that the alternatives are very different, raising the traditional challenge of how you compare “apples with pears” (noting in passing that these two fruit are far more similar than our alternatives). In LCA, we establish a neutral system boundary for our study that does not favour any alternative, and that is the basis for the comparison. In this instance, we chose to start our system with a pile of household waste, and to follow it through until it had been landfilled, incinerated (with energy recovery), recycled (to the point where it is no longer waste) or “lost” (e.g. by evaporation in composting processes). Any energy or recyclate produced would be credited with the avoided impacts of having to make the output by traditional means.

The top-level results, associated with handling one year’s waste capacity for the HERU (2.2 tonnes), are presented in the table below, showing the environmental impacts of the three scenarios against the six indicators used. For global warming, we see that the HERU delivers the greatest carbon benefit, offsetting (negative figure) about 300kg CO2-eq (a ~25% improvement on the alternatives). The HERU also outperforms the collection scenarios for the two indicators of toxicity potential, to humans (HTP) and freshwater species (FAETP). In contrast, the collection scenarios fare better for the potential to cause acidification and eutrophication, and to deplete abiotic resources.

Impact Category Code Units HERU Co-mingled K S-sort
Global Warming Potential GWP kg CO2-eq -295 -175 -223
Acidification Potential AP kg SO2-eq 0.6 -1.2 -1.5
Eutrophication Potential EP kg PO4-eq 6.82 0.22 0.14
Human Toxicity Potential HTP kg 1,4-DCB-eq -1,560 -1,055 -1,137
Abiotic Resource Depletion ARD kg Sb-eq -3.7 -5.6 -5.7
Freshwater Aquatic EcoToxicity Potential FAETP kg 1,4-DCB-eq -117 -81 -89

These results are typical for LCA studies, where very different systems can lead to varying environmental impacts against the range of criteria studied. Our detailed results clarified for Nik where the environmental “hot spots” (and “sweet spots”) lie for each of the three systems. As he continues his product development, he can target his hot spots and look to further improve the environmental credentials of the HERU. Ricardo’s LCA work has shed a whole new perspective on his technology:

“I really valued Ricardo’s impartial assessment and practical LCA expertise. The study substantiated my belief that the HERU can make a significant contribution to climate change mitigation. I’m looking forward to improving our results even further during the next round development.”

To find out how you could challenge, investigate and improve your product’s green credentials using LCA, please get in touch with Simon Gandy.

If you would like to read Ricardo's report on the HERU, it can be downloaded in full from their website here: https://www.myheru.com/life-cycle-assessment-heru/