Feasibility of lactic acid production from cereal milling residues in the UK

Abstract

The production of poly-lactic acid (PLA), a biodegradable and bio-based polymer, from cereal milling residues (wheat, barley, oat, starch) at large scale represents a market opportunity in the UK, provided five crucial parameters are in place: 1) a supportive political framework, 2) market attractiveness, 3) technological feasibility, 4) feedstock availability, and 5) economic viability. In consideration of these parameters, this study assessed the potential for developing a UK lactic acid (LA) plant capable of providing sufficient LA for a 30,000 tonnes per year (tpa) PLA plant, utilising cereal milling residues as feedstock.

A review of the EU political framework for bio-based products and evaluation of the existing and near-future PLA market demonstrated that a supportive environment exists in the UK for large-scale production of LA. Brand owners are continually seeking to demonstrate their products are environmentally sustainable through introducing bio-based ingredients and bio-based packaging, while consumers are increasingly keen to support environmentally-friendly products. In accordance, the PLA market in the EU is expected to grow 13% by 2025, with demand expected to outstrip supply. Meanwhile, growing competition between food markets and industry for traditional agricultural crops have meant that utilisation of non-food cellulosic feedstock is becoming increasingly attractive. As a consequence, there can be expected to be high future demand in the EU for LA derived from cellulosic biomass.

To date, there has been little activity in developing LA from milling by-products. However, by analysing the technologies and production pathways needed for production of LA and PLA from cereal residues, we found numerous technologies that have been commercialised for LA and PLA production from cellulosic biomass and several processes that have focused on the conversion of milling residues to fermentable sugars, thus indicating technical feasibility. In consideration of these processes, a potential production pathway for conversion of milling residues to LA was constructed.

This study further demonstrates that there is good potential in the UK for developing value chains based on production of LA from cereal milling residues – notably wheat bran/middlings and oat husks/hulls – in sufficient volumes to supply a 37,500 tpa LA plant (equivalent to the feedstock requirement of a 30,000 tpa PLA). Most encouragingly, it was discovered that a single oat milling facility exists in the UK which alone produces almost sufficient residue volumes to supply a facility of this scale.

Ultimately, this study shows that there is a strong and growing market for LA and PLA, the production pathways from cellulosic feedstocks are becoming commercialised and therein lies potential to develop value chains from cereal milling residues in the UK. However, little work has been done to date regarding the manufacture of LA from milling residues, and therefore this opportunity can be expected to have significant risks, especially in regards to technical feasibility.