Validating low carbon bio-renewable alternatives to petrochemicals: exploring end of life impacts

A need to reduce anthropogenic carbon emissions has prompted a trend for industry to switch from fossil to biorenewable feedstock, but it remains unclear if this is always a ‘low carbon’ decision. The concept that biomaterials can have lower greenhouse gas (GHG) emissions than petrochemicals has been grasped enthusiastically, however one aspect in particular has been somewhat overlooked when considering life time emissions; their disposal. Low carbon waste management is not a new concept, but its application to waste streams with high bio content is not well understood. This thesis employs mixed methods to investigate the impact of end of life scenarios on the GHG emissions associated with biorenewable materials. A hybrid life cycle assessment (LCA) of a biomaterial and petrochemical product shows that end of life scenarios have a bigger impact on overall GHG emissions for waste biomaterials than those based on petrochemicals and shows that biomaterials can be lower carbon if disposal is taken into account. In order to understand how such benefits from biomaterials can be realised, fourteen interviews with biomaterial industry stakeholders were then conducted and provided insights from which policy options to promote low carbon disposal are developed. A focus group with nine experts considered these options and made recommendations to raise the profile of disposal via encouraging product purity, stimulating demand and updating collection infrastructure. One other recommendation was to provide more transparency regarding the benefits of particular disposal options on specific biomaterials and in order to help with this the final part of this thesis is devoted to the development of a low carbon decision support tool for biomaterial disposal options based on LCA and tested on two hemp biorefineries. This tool was used to rank all the disposal options according to GHG emissions as well as cost effectiveness, particularly useful in locations where preferred strategies may not be available for example where there is no district heating infrastructure to support Combined Heat and Power (CHP). Its results confirm the waste hierarchy but also shows novel technologies such as ‘ethanol from waste’ are can be both low carbon and economically competitive. This tool can both help biorefinery operators to design low carbon disposal options into their products, as well as help guide waste and biomaterial policy decisions. The tool suggests that existing UK disposal infrastructure for municipal solid waste streams is not designed with biomaterial waste in mind, and that a rethink in waste disposal and its funding may be required to ensure future bio-based economies achieve better reductions in carbon emissions.