Green waste and other organic side streams can be valorised as energy, compost, fertiliser, cattle feed and ingredients for high-quality chemicals. Owing to their highly divergent properties, however, the by-product streams require a custom approach. With insect larvae as an interim step, this problem disappears, which enbables a refinement process with a single inflow. VITO is investigating the fractionation of the various larvae components within this process.
Insects are gaining more and more attention as an alternative source of biomass, nutrients (mainly proteins) and other useful substances. The major advantage is that insects generally see strong and easy growth, without taking up much space. Moreover, most species are not too discerning about what they eat. This presents the prospect of valorising highly divergent organic by-product streams such as grass, fruit and vegetable waste, whose direct processing would normally depend very much upon intrinsic properties, and which is also seasonal.
Fractionation
The use of insects can bring together a range of side streams, processing them together in a single bio-refinery – which obviously makes the economic valorisation much more interesting. This approach formed the basis of the European Horizon 2020 project InDIRECT, which ran from late 2016 to late 2019 and examined the potential of (larvae of) the black soldier fly and the mealworm fed on various by-product streams. VITO brought together a consortium of nine partners for this.
Insect larvae consist of fats, proteins and chitin: three (from a human perspective) useful substances which, before they can be used, first need to be separated and cleaned up – or ‘fractionated’. VITO was responsible for this within the InDIRECT project. ‘We have a lot of experience in terms of separating components and cleaning them up, partly through our research into micro-algae,’ says Leen Bastiaens from VITO. For the fractionation of the larvae biomass, VITO built its own installation on its site, known as the fractionation pilot plant (which is part of the Insect Pilot Plant). Within InDIRECT, the larvae were supplied by two industrial insect farms: Protifarm and Circular Organics. VITO carried out the applied research into the components it was fractionating in collaboration with the companies Nutrition Sciences, Chemstream and the Innovation Support Point.
Unique process
The fractionation at VITO takes place in several steps. First, a mechanical process – compression – is used to separate the hard skeletal structures of the larvae. These largely consist of chitin, which is the most common biopolymer on Earth after cellulose. The chitin can then be broken down into short sugar chains, which presents the prospect of a wide range of applications. The VITO process that separates and processes the chitin is practically unique. ‘Chitin is seldom fractionated and characterised on this scale,’ says Bastiaens. ‘Over the three years that the project ran, we processed more than a ton of larvae. That means we have definitely taken the step from lab to pilot scale.’
The scale-up is important, even though the technology remains in a largely exploratory research phase. ‘Countless kilos of a particular ingredient can sometimes be needed for the current applied research,’ continues Bastiaens. ‘That means it helps if you're already able to work with reasonable volumes. Furthermore, it brings us closer to realistic circumstances.’ Besides scaling up, custom fractionation (tailoring) is also important. ‘If we're looking to make feed for young chicks, for example, there should not be too many salts or specific tastes in the end product. Some things we can do to avoid this are to modify the larvae's food – i.e. the by-product streams – or to make alterations to the bio-refinery. The precise influence of the composition of the streams on the larval growth and on their own composition was researched in detail.’ According to Bastiaens, further research into the metabolic properties of the larvae may lead to an exhaustive optimisation of the growth and the tailoring.
Alterations to legislation
Could the interim step via the larval growth – hence the project name ‘InDIRECT’ – make the valorisation of organic by-product streams economically profitable? In order to create a sustainable alternative to e.g. imported soya from Brazil or basic fossil chemicals? ‘At present, not yet’, admits Bastiaens. ‘There are too many steps that still need automation.’
But the legislator may be able to lend a hand, for example by permitting the use of larvae in cattle feed. For the time being, this is not always allowed, because insects currently still fall under the strict animal laws – and there have been very strict rules on the use of animal products in the agriculture and food sector since mad cow disease in the 90s. Bastiaens does expect this to change at a European level soon, though. ‘Insects as a raw material for cattle feed will first be permitted for broiler chickens and pigs – for egg-laying chickens and aquaculture it's already allowed. It might well be a bit too sensitive for cattle yet.’
A wider view of the applications could also help. It was possible to demonstrate for various components of larval biomass, for example, that they have an antimicrobial and prebiotic effect. This is interesting for the production of high-quality cattle feed. Additionally, countless components are usable for pharmaceutical products and cosmetics.
In the meantime, VITO is ready to support companies that are interested in the valorisation of by-product streams through larval growth via contract research. ‘We're noticing that interest from the industry is increasing. That's obviously the intention of our VITO activities. By investing in this research infrastructure, such as the fractionation pilot plant, we're aiming to raise companies' interest in starting to do their own work around this in turn,’ says Bastiaens.
