Despite global efforts to promote recycling and build a circular economy, certain types of waste often slip through the cracks due to their perceived difficulty and expense to treat. Wet wastes, characterised by high water content, including food and agricultural waste, sewage and oil sludges, fall into this category.
With more than 80 per cent of the world’s wet waste ending up incinerated, landfilled, or illegally dumped, the environmental and financial costs are staggering. However, amidst these challenges lies a promising opportunity for those willing to innovate and transform wet waste into profit.
The challenge of wet waste
Wet waste presents a unique challenge due to its exceptionally high water content, often exceeding 80 per cent of the waste’s mass. This not only adds to disposal costs but also requires energy-intensive methods to remove excess moisture. Understanding the sources and compositions of various wet waste streams is crucial for developing effective treatment solutions.
Food and agricultural waste
According to the United Nations Environmental Programme (UNEP) Waste Index Report 2021, an estimated 931 million tons of food waste was generated in 2019, with households, food service, and retail contributing significantly.
In parallel, agricultural waste, encompassing materials from farming, livestock rearing, and processing, presents substantial challenges. In China alone, agricultural waste production reaches 759 million tons, contributing to 17 per cent of the global waste volume.
The diverse composition of food and agricultural waste, coupled with high moisture content and microbial activity, exacerbates treatment complexities. Contamination from food packaging and the sheer volume of waste further compound these challenges, making management and disposal efforts logistically and environmentally taxing.
Sewage and oil sludges
Sewage sludge, also known as bio-sludge, arises as a by-product of wastewater treatment processes. With annual production estimates reaching 1.6 billion tons, sewage sludge management becomes increasingly challenging.
Similarly, oil sludge stemming from oil refining and industrial processes presents significant hurdles. Classified as hazardous waste, oil sludge production amounts to approximately 22.3 million tons annually.
Managing sewage and oil sludges entails careful handling and disposal methods to mitigate environmental and health risks effectively.
Also Read: WasteX nets funding to help farm producers convert biomass waste into biochar
Why current solutions fall short
Traditional methods like incineration, composting, and landfilling are commonly used for wet waste management but have significant drawbacks.
Incineration reduces waste volume and can produce energy but emits air pollutants, harming human health and the environment. It is inefficient for wet waste as 30 per cent of the energy goes into drying, and the generated ash residues require landfilling.
Composting, relying on microbial activity, turns organic matter into compost. However, it requires time and space, and not all wet waste is suitable, leading to odour, pest issues, and nutrient runoff.
Landfilling, while convenient, produces methane, a potent greenhouse gas and leachate that contaminates soil and groundwater, requiring extensive monitoring and maintenance to prevent environmental harm and health risks.
Alternative solutions lack scalability and efficiency
Alternative methods like anaerobic digestion, pyrolysis and gasification, and black soldier fly larvae treatment offer solutions but face scalability and efficiency challenges.
Anaerobic digestion, a biological process, produces biogas and digestate but requires long processing times and the residual waste requires further treatment or disposal.
Pyrolysis and gasification are thermochemical processes that convert waste into syngas and biochar or ash residues. However, they demand extensive drying, adding to operational costs.
Black soldier fly larvae treatment involves feeding organic waste to black soldier fly larvae, which consume the waste and convert it into insect protein. However, the treatment process lacks flexibility, scalability and efficiency for large-scale applications.
Although various methods exist for managing wet waste, each comes with its own set of challenges and limitations. Innovative solutions are needed to address these shortcomings and pave the way for a more sustainable approach to waste management.
How hydrothermal technologies can redefine the landscape
Hydrothermal technologies offer a promising avenue for revolutionizing the treatment and utilization of wet waste streams. Unlike traditional methods that often face scalability and efficiency issues, hydrothermal processes leverage the unique properties of pressurized hot water to efficiently break down organic matter into valuable resources.
Understanding hydrothermal technologies
Hydrothermal technologies function by subjecting wet waste to heat and pressure, altering the properties of water within the waste. This transformation enables water to act as a potent solvent, catalyst, and reactant in chemical reactions, enhancing the breakdown of organic compounds. As a result, hydrothermal processes achieve higher efficiency in converting wet waste into valuable end products, including biofuels, biochemicals, and biochar.
Also Read: Rethinking wastewater treatment to support Singapore’s ambitious water goals
Diverse applications of hydrothermal technologies
Hydrothermal technologies encompass various methods tailored to specific process conditions and desired outputs. For instance, hydrothermal oxidation enhances biodegradability or eliminates hazardous waste, while thermal hydrolysis upgrades low-value oil. Recent focus has shifted towards hydrothermal conversion processes like hydrothermal carbonization, liquefaction, and gasification, which hold significant promise for transforming wet waste into fuels.
Competitive advantages of hydrothermal conversion
Hydrothermal conversion processes offer several competitive advantages.
- Enhanced efficiency: By utilizing water content within the waste, hydrothermal conversion eliminates the need for energy-intensive drying, resulting in higher efficiency compared to traditional methods.
- High space-time yield: These processes boast rapid processing times, enabling the treatment of large volumes of waste within a compact footprint.
- Versatility: Hydrothermal conversion processes accommodate a wide range of wet waste streams, addressing diverse environmental and economic challenges.
- Resource recovery: Valuable resources, such as fuels, chemicals, and minerals, are recovered from wet waste, promoting resource conservation and circular economy principles.
- Biological safety: The sealed, high-pressure environment of hydrothermal conversion processes ensures biological safety, eliminating exposure to biological risks and effectively sterilizing the waste.
- Reduced environmental impact: Unlike conventional methods like incineration or landfilling, hydrothermal conversion produces clean emissions and effluents, minimizing environmental harm.
Advancements and future directions
Recent strides in hydrothermal technologies are centred on enhancing efficiency, scalability, and versatility across a spectrum of waste streams. Innovations in reactor design, process control, and feedstock diversification are propelling advancements in this domain, offering transformative solutions for wet waste management.
Altent Renewables, a Singapore-based startup, has developed a proprietary hydrothermal process designed to convert wet waste into syngas and minerals. Syngas, a blend of hydrogen, methane, carbon monoxide, and carbon dioxide, has a multifaceted utility as a fuel gas. It can be harnessed for heat and electricity generation while also serving as a fundamental building block for various fuels and chemicals. These include pure hydrogen, methanol, ethanol, and sustainable aviation fuels, positioning Altent Renewables at the forefront of sustainable energy innovation.
Altent Renewables has conducted extensive testing of their technology in a lab-scale facility, employing various waste streams, including food waste, bio-sludge, and oil sludge. Encouraged by positive outcomes, they are now moving forward with scaling up to a pilot plant.
This phase marks a crucial step towards commercial viability and widespread adoption of their innovative hydrothermal process. By implementing their technology, businesses can potentially reduce wet waste disposal costs by more than 70 per cent, achieving both economic and environmental sustainability.
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This article was first published on April 24, 2024
The post Unlocking hidden gold: How overlooked wet waste streams hold profit potential despite challenges appeared first on e27.