Efficiency is paramount in any manufacturing process. The line between starting material and final product should be as straight as possible with interstitial materials jettisoned as waste to maintain optimal flow. Yet, a circular economy necessitates considering waste streams as a commodity and determining their potential value.
Taking trash off someone’s hands is only the first step, the next is figuring out a process to make it lucrative. In the last three years, more companies have acquired the investments necessary to turn waste into something valuable.
"When resources are limited and you are discarding some nutrient that has a sale price associated with it, there is value in looking at the processing to find a way to capture everything," says Senya Joerss a technical manager in fish processing, who recently launched CFS Guru, a food and supplement industry consultancy. "For example, trim and other materials from cutting a fish filet are a globally recognized commodity. But there are parts of that process that could be improved to make aquaculture feed higher in protein."
The trend of converting waste streams to profit is being applied to food, chemicals, and fuel with the potential to make significant contributions to a circular economy. Experts acknowledge that bioenergy and biotechnologies would benefit from valorizing underused biomass resources. A new cluster of start-ups has identified financial opportunities in everything from food waste to municipal sludge, landfill gas, animal manure, industrial organic wastewaters, and organic fractions of sorted municipal solid waste.
A collaboration of multiple US government agencies known as the Biomass Research and Development Board, said in a report that "in addition to improving economic value, reliability, and availability of aggregate biomass resources, waste streams can supplement or be blended with traditional biomass feedstocks, which directly contributes to the viability, quality, and resilience of individual biomass supply chains (https://biomassboard.gov)."
For a decade, the private sector has hesitated to invest in scaling-up advanced technologies. Price parity of biotech products, along with policy-related market uncertainty and land availability for non-food crops slowed investment in largescale biorefineries that would require a billion tons of biomass to produce fuels and bioproducts. Now, processing experts are developing solutions to turn waste streams into valuable starting materials for biomanufacturing.
MANUFACTURING BIOFUELS FROM SEWAGE
"Now is the time for this kind of technology," says Michael Paszti, chief operating officer at Carbon Critical, a start-up taking the biosolids leftover from municipal treatment plants and processing them into drop-in biofuels. "The world changed when lawmakers created the Inflation Reduction Act (IRA) in the US and its equivalent programs in other countries."
The Inflation Reduction Act was signed into law on August 16, 2022, and included more than $60 billion to support "on-shore clean energy manufacturing in the US." Incentives in the bill encouraged an expansion of green hydrogen and green fuel production.
According to the US Environmental Protection Agency, the largest contributor to global greenhouse gas emissions is energy production and use, including fuels that power vehicles and buildings (http://tinyurl.com/mubxr5j8). The agency indicates that three sectors—transportation, electric power, and industry—generate about 25 percent of national emissions (http://tinyurl.com/2unmk5sc).
"Taking waste and turning it into a drop in fuel is really the ultimate in terms of ecological solutions," says Paszti. "It solves two problems and makes money on the input and the output."
Municipal organic waste disposal has become more expensive with the advent of emissions standards, because if it is not disposed of properly it turns into methane, a greenhouse gas. To avoid high fines for improper disposal, sewage treatment plants typically pay third parties to remove and discard their biosolids according to regulatory guidelines. However, instead of disposing of the waste, Carbon Capture processes it into biofuel.
Supercritical water pyrolysis (SCWP) is a highly efficient process that can be used to breakdown biosolids after industrial wastewater treatment. Unlike other wastewater treatment techniques like physical, chemical, and biological treatment systems, supercritical water pyrolysis detoxifies and remediates a wide range of organic pollutants. SCWP technology relies on the unique properties of supercritical water which has high diffusivity, low viscosity, zero surface tension, a controllable dielectric constant, fewer hydrogen bonds, and miscibility with organic waste and oxygen.
Using a technique called the Paszti-White process, Carbon Critical takes the carbon-rich SCWP product and generates a mixture of gases and bio-oil. Hydrogen is then extracted from the mixture and used to deoxygenate the bio-oil stream, converting it into transportation fuels.
"From a biosolid slug you generate a liquid phase and a gas phase," says Paszti. "Then you recombine them to give you the final fuel at the end." He says there is no fantastical, Star Trektype technology involved. The whole process depends on wellknown equipment used in a specific way, reconfiguring and combining existing technologies. He says the plant is under construction overseas and before the summer will be relocated to the site of their pilot plant in North America.
PANNING THROUGH FOOD PROCESSING WASTE
Waste is produced at every point of the food production process. The UN estimates that between harvest and retail we lose 13 percent of all food. A growing number of companies are investigating how to turn food processing side streams profitable. The food industry has a term for making food waste useful; they call it upcycling. The specific definition of the term depends on the source. According to the Upcycled Food Association (https://www.upcycledfood.org), "upcycled foods use ingredients that otherwise would not have gone to human consumption, are procured and produced using verifiable supply chains, and have a positive impact on the environment."
Some companies are adapting agricultural side streams into ingredient sources. They scavenge anything left over from the production process, such as corn cobs from corn canning facilities and oat hulls from oat processing facilities and extract the remaining nutrients. Since biorefineries rely on a sugar or starch based medium, one recently launched start-up hopes to take food processing wastewater and sell it as microbe feed.
Last summer, the company Hyfé announced it had raised over $11 million from investors to transform food processing wastewater into biomanufacturing feedstocks (https://hyfe.tech). In an interview with AgFunderNews (http://tinyurl.com/29wp9d87), the company’s co-founder, Michelle Ruiz said, "It is critical for the feedstocks that will power that growth to come from underutilized waste carbon streams that are cost effective, non-competitive with food, and avoid disruption of agricultural systems."
Hyfé plans to co-locate their processing units on the site where the food processing waste is created before it is sent to a waste treatment facility. They will then remove the valuable compounds from the water and return it clean to the manufacturing site. Ruiz says, their process will end up saving the facilities millions of dollars that would normally be spent on wastewater management, particularly for heavy water users. She adds that her company’s technology frees up wastewater infrastructure capacity, allowing for production expansion.
For cultivated food to achieve price parity as a norm, Ruiz said, current feedstocks must be multiplied. She believes Hyfé has identified an opportunity to provide a solution by turning food processing waste into a reliable supply of bioreactor feed.
MORE TO CONSIDER
However, before non-conventional feedstocks—whether originating from industry, agriculture, or municipality—can be regularly used in the food supply a level of precaution is needed.
"From my experience in the waste industry, you do not get to pick what waste you get," says Paszti. "You are the garbage man. You take whatever the customer wants to give you."
Hence, replacing refined sugars with cheaper, complex feedstocks from agricultural side-streams means considering safety precautions throughout the entire biotechnological conversion process. According to a team of researchers at Wageningen University, processors need to realize that the unknown quality of less defined feedstocks means safety issues might arise for bioreactors (http://tinyurl.com/8uss9p63). The composition of these feedstocks might be inconsistent or contain contaminants that can affect the reproducibility of the microbial cell factory process. To ensure product safety and prevent undesired toxic side products, companies will have to handle non-conventional feedstocks differently. Yet, analyzing these feedstocks has its own challenges.
"There is a scientific challenge associated with testing for a component when it is diluted in so much water," says Joerss. Depending on the analyte, it could be undetectable and/or degraded making analysis laborious and irreproducible. "If you have a lot of water, it is difficult to find a lab that is able to test for the component you are looking for because it is so diluted," she says. For a small company that type of analysis could be cost prohibitive, and she adds, you still cannot be sure you are getting an accurate measure of what components are present.
Joerss says that there are companies interested in recovering protein from seafood processing wastewater, for instance, but it is expensive to test the amino acid profiles of such a dilute sample. And even if a small processor accomplishes the analysis, they still might not recover enough protein from the water to make the effort worthwhile. "When quantity matters, reusing wastewater might not be lucrative for smaller processors," she says.
"The best chance at success might come from letting third-party, recovery companies who have worked with waste streams and understand the importance of protein quality fine-tune protein extraction methods from side streams," Joerss said. That is the exact business model Hyfé is betting on.
ACHIEVING A CIRCULAR ECONOMY
Valorizing waste will no doubt be a necessary step towards creating a sustainable, circular economy, whereby we keep resources in use as long as possible. The alternative linear economy, where we ‘make, use and dispose,’ has only resulted in decades of a global waste problem.
Across the supply chain in the US, food is wasted at a rate of 2 percent by manufacturers, 16 percent by farms, 40 percent by restaurants and food services, and 43 in homes (https://www.rts.com/resources/guides/food-waste-america/). Although household food waste is the biggest problem, addressing the difficulty of sorting bulk waste—composed of plastic, paper, and metal—prior to downstream processing prohibits a simple solution, for now. Despite (or maybe, because of) manufacturers being the most efficient in terms of waste reduction, a circular economy will start with processors.
Currently, food processing solid wastes are mostly landfilled or composted, while liquids are washed down sewers and either pass through public wastewater treatment systems or released directly into natural waterways. They largely contain biodegradable organic matter comprised of fats, oils, protein, carbohydrates, pigments, flavonoids, or antioxidants, with variable amounts of suspended solids. So far, processors are focusing on anaerobic digestion and fermentation as a means of profiting from these waste streams.
The anticipated growth of the biotech sector will only be possible if the biomass supply chain consists of more than just conventional crops. The bioeconomy would never be deemed a success if it were to cause greater nutrient runoff, soil disturbance, conversion of fragile lands, and water use.
Non-food crops capable of thriving on marginal lands, require fewer resources for production and could help reduce nutrient runoff, soil erosion, and water usage relative to food crops. In addition, as described in this story, using diverse sources of renewable biobased feedstocks—such as manures, biosolids, food waste, and sorted municipal solid waste—could help to reduce greenhouse gas emissions, management costs, and water quality degradation, as well as provide revenue streams and renewable energy.
Hence, more testing will be needed to ensure environmental and human health safety when using non-conventional feedstock for bioreactors. And even after cultivation any remaining biomass becomes waste that will need to be disposed of or re-used in a safe way. Processors will have to acknowledge that some green processes, even some waste disposal methods, still have detrimental effects on the environment. And a circular economy must rely on a spectrum of waste conversion solutions.
The United Nations’ Sustainable Development Goals (https://sdgs.un.org/goals) would reduce food losses during post-harvest processing, production, and supply chains by 50 percent, in addition to cutting the food waste produced at retail and consumer levels by the same amount (http://tinyurl.com/rsxkn79d). The US has committed to reducing personal food waste by half in the next seven years (http://tinyurl.com/8ss4wr3m). The European Union has also developed waste policies regarding environmental action plans and legislative frameworks (https://doi.org/10.1016/j.seps.2021.101222). These initiatives are likely to push the world closer to a circular economy while reducing the environmental impacts of our energy production and consumption putting us in a better position to address resource scarcity issues in the future.
About the Author
Rebecca Guenard is the editor-in-chief of INFORM magazine. She can be contacted at rebecca.guenard@aocs.org
