How to Upcycle Agricultural Biomass
South East Asia is adopting biological solutions to turn agricultural biomass into high-value products, drive a circular economy, and combat climate change.
Southeast Asia stands as one of the largest and most diverse agricultural markets globally. Encompassing a wide range of farmland and agricultural practices, each country within the region exhibits significant variations in production. With eight out of ten countries heavily reliant on agriculture, Southeast Asia emerges as a key producer and exporter of commodities like palm oil, rubber, rice, and sugar.
As a consequence, there is a considerable amount of ‘waste’ agricultural biomass such as empty fruit bunch, palm kernel cake, rice straw, and bagasse generated annually. A significant portion of this is either disposed of or utilized in low-value applications such as mulching.
But biological solutions, which combine biology and technology, offer alternative pathways. Harnessing enzymes and microbes offer remarkable opportunities for upcycling agricultural biomass into high-value products.
Small size, transformative power
Enzymes, as biologically active proteins found abundantly in nature, play a crucial role in catalysing chemical reactions. They accelerate and regulate the conversion of one substance into another, a process known as catalysis. Each enzyme is specialized to break down specific substances.
In industrial applications, enzymes find wide use. For instance, oxidoreductase enzymes in bakeries reduce reliance on chemical oxidants. Isomerase enzymes are employed in the starch industry to produce fructose. Brewers use lyase enzymes to enhance fermentation capacity and ensure consistent flavour profiles in their beer.
Microbes, on the other hand, encompass bacteria and fungi, omnipresent in our environment, the food we consume, the air we breathe, and our bodies. While often associated with dirt and disease, many microbes are beneficial. In nature, they aid in the decomposition of organic matter. Within our bodies, beneficial microbes aid in digestion and protect against harmful invaders.
In industrial and agricultural settings, microbes play pivotal roles. In livestock production, they support animal health and nutrition, reducing the need for antibiotics in poultry. In agriculture, they assist farmers in increasing yields and safeguarding crops.
Answer to second-generation ethanol production
Rather than remaining as waste with no environmental value, biological solutions now enable the conversion of agricultural biomass into cellulosic ethanol, also known as second-generation ethanol. Unlike first-generation ethanol, derived from food sources like starch and sugar, which often sparks debates over food versus fuel, second-generation ethanol generally enjoys a more positive perception worldwide.
To facilitate enzyme activity, agricultural biomass must undergo pulping through pre-treatment. This step is crucial as it prepares the biomass for subsequent processes, ultimately leading to higher yield production. Pre-treatment alters the size, structure, and chemical composition of the biomass and involves various methods such as steam explosion, acid treatment, alkaline treatment, organic solvents, or combinations thereof.
Following pre-treatment, enzymes hydrolyse cellulose and hemicellulose into simple sugars. Cellulolytic and xylanolytic thermostable enzymes efficiently break down cellulose and hemicellulose components, converting pre-treated biomass into fermentable sugars like xylose (C5) and glucose (C6). Optimal enzyme hydrolysis conditions typically involve operating at temperatures of 50–55°C and pH levels of 4.7–5.2, although specific conditions may vary based on substrate and process parameters.
Historically, ethanol yield was limited due to challenges fermenting C5 sugars. However, advancements, particularly the use of selectively bred yeast strains capable of tolerating high levels of inhibitory compounds found in cellulosic hydrolysate, have overcome this hurdle. Specialized yeast strains enable co-fermentation of both C5 and C6 sugars, with rapid xylose utilization and high cellulosic ethanol yield. Similar to first-generation ethanol production, cellulosic ethanol is recovered through distillation from the fermentation broth, while thin stillage and lignin cake serve as valuable co-products.
Cellulosic ethanol offers significant environmental benefits, reducing greenhouse gas emissions by over 60% and 80% compared to first-generation ethanol and gasoline, respectively. Additionally, it boasts a higher-octane number, enhancing engine performance and blending properties. Although it seems like fiction, Green Cop, a Singapore-based startup specializing in sustainable fuel solutions, is collaborating with a leading global palm oil player to convert empty fruit bunches into sustainable biofuels.
Repurposing biomass for poultry feed production
Broiler meat is the staple food in Southeast Asian nations like Indonesia and Malaysia. These countries heavily depend on imported poultry feed to ensure a steady chicken supply. In 2023, the combined imports of soybean meal for their poultry industry reached over 7 million tons in both countries.
Conversely, Indonesia and Malaysia, the world’s top two palm oil producers, yield over 7 million tons of palm kernel cake (PKC) annually — a byproduct of palm kernel oil extraction. PKC is predominantly exported as low-cost cattle fodder to distant markets like New Zealand, South Korea, and Europe, where it serves as a source of protein, fats, and energy in cattle feed.
To date, PKC usage in poultry feed has been limited due to its high fibre content, primarily composed of insoluble mannose-based polysaccharides unsuitable for monogastric animals like poultry. However, advancements in biological solutions are changing this narrative.
PKC must first undergo grinding to enhance enzyme accessibility to its fibres. Following the grinding process, enzymes are introduced in a liquefaction process to break down glucomannan and cellulose in the ground PKC at temperatures ranging from 50 to 60°C, yielding mannose and glucose, respectively. The resulting liquefied slurry is then cooled to around 30°C before yeast is added to ferment these simple sugars (producing Ethanol as a by-product!). This step is crucial as excessive sugar intake can disrupt the balance of beneficial gut bacteria, leading to dysbiosis. The palm kernel pulp obtained after fermentation must be dried before being used as poultry feed.
The resulting dried palm kernel pulp exhibits decreased fibre content and increased levels of protein and fat. Consequently, it can serve as a viable alternative to soybean meals and corn distillers’ dried grain in broiler diets, offering comparable performance outcomes without adverse effects.
Furthermore, repurposing PKC not only reduces dependence on imported feed, thereby saving carbon emissions associated with shipping but also serves as a substitute for fossil fuels through ethanol production, potentially decreasing approximately 660 kg CO2-eq per ton of upgraded PKC. Although commercial plants for PKC-to-poultry feed conversion are yet to emerge, we anticipate their establishment in the region soon.
Waste not, want not
Agricultural biomass was traditionally considered waste, presenting a hurdle for producers. Yet, with the emergence of biological solutions, there’s an opportunity to transform this biomass into valuable products. Encouraging industry players to embrace these changes is crucial, and incentives can play a pivotal role in driving this transition.
For instance, green financing can facilitate the acceleration of biomass upcycling by granting companies access to low-interest funding. Tax credits for companies investing in biomass conversion technologies can substantially decrease initial costs, rendering the investment more attractive. Additionally, subsidies for research and development in sustainable agricultural practices can expedite innovation and the adoption of new technologies, ensuring a smoother and quicker transition to a bio-based economy.
By incentivizing industry players to embrace these innovative practices, we can promote a circular economy in the region, create new income streams, and enable Southeast Asian nations to contribute to climate change mitigation by offering lower-carbon alternatives.
