BIOBASED CHEMICALS
of sustainable aviation fuels , but at what cost to agriculture ?
In this context , non-edible feedstocks and waste biomass that is rich in renewable carbon and not competing with food production have become very important , offering an attractive , green solution for sustainable chemical production . This route provides a huge opportunity for the chemical industry to adopt a new circular economy model , making constructive use of the vast quantities of waste generated by societies .
Use of microbes
The feasibility of a chemical biorefinery is essentially dependent on a continuous and low cost supply of biomass along with cost-effective pre-treatment and saccharification for the extraction of fermentable sugars . The source of the biomass opportunity is in the nature of microbes themselves .
Microbes are amazing creatures that make use a diverse range of metabolic patterns to be able to survive in different environments : they adapt quickly , they have the ability to synthesise and they accumulate a variety of molecules to operate as ‘ cell factories ’ in themselves . For our purposes , that means that we can engineer the organisms involved to become even more efficient and targeted in their re-processing of materials into useful chemical elements .
In turn that means cleaner synthetic methods , an intensification of processes and a way of minimising waste from materials and producing high value products . Current projects include making biobased products like xylitol , 2,3-butanediol ( BDO ), and itaconic , lactic and succinic acids from a variety of waste streams from agro-industrial sectors and supply chains . These include sugarcane , brewers ’ spent grains , crude glycerol and unconsumed food .
Bread to chemicals ?
Bread waste is a good example of what is possible . In the UK alone , around £ 20 billion worth of food and drink are wasted every year . A staple food like bread , with its relatively short shelf life and commercial overproduction , is a major part of that waste . An estimated 10 % of total bread production is wasted during the supply chain .
In households it is the second most wasted food product , according to WRAP figures in 2021 , equating to 20 million slices / day .
Lab-scale production of biochemicals using low-cost bread waste , which is a rich source of high-quality , fermentable , food-grade sugars in addition to other nutrients , is as good as pure carbon sources . Bread waste , generally , has a homogenous and consistent composition . The sugars are ‘ clean ’ as they are devoid of inhibitors , and their recovery is convenient , not involving the need for any harsh pretreatment processes
Bread waste has been employed as feedstock for high level production of platform and commercially important chemicals , including 2,3-BDO , ethanol , and both lactic and succinic acid . The presence of one or two functional groups makes these molecules versatile for chemical transformation and enable diverse applications .
For example , lactic acid ( LA ) has many applications across the food , pharmaceutical , cosmetics , food , speciality chemicals , textiles and leather . With the growing demand for biodegradable polymers using LAs , the global market value is expected to be $ 9.8 billion by 2025 .
In tests , the fermentation of bread waste using enzymatic hydrolysate generated ~ 155 g / L of LA , 139 g / L of BDO and 115 g / L of ethanol . In addition , the residues generated during the process yielded substantial amount of biomethane . Extrapolation of these results shows that 150- 500 kg of these products can be manufactured from every one tonne of bread waste , depending on the starch content .
Bio-renewables are an obvious and practical solution , but while petrochemicals remain cheaper , the transition to a sustainable and circular model is going to be slow and it needs to be accelerated . The chemicals industry needs to be bold enough to lead change , to establish larger-scale production models with lower costs . In this context , government subsidies to spur industry take-up would make a real difference . ●
Dr Vinod Kumar
SENIOR LECTURER
CRANFIELD UNIVERSITY k + 44 1234 754786 J vinod . kumar @ cranfield . ac . uk j www . cranfield . ac . uk
ESTABLISHED 1981