Energy Recovery from Waste Sources: Anaerobic Digestion and Waste Heat Recovery

In order to reduce global energy consumption and greenhouse gas emissions, sectors like agriculture (11% of all global emissions) and manufacturing (12% of global emissions) will need to leverage innovative solutions to reduce the amount of carbon dioxide emitted and energy lost. Technologies that recover energy from a variety of sources including organic waste and waste heat will be needed to support companies and governments looking to achieve net zero. 

heat recovery system in a building

Additionally, due to the global demand for renewable energy and carbon neutral solutions, there has been an increased demand for biomethane (also known as renewable natural gas - RNG). The demand for biomethane has been bolstered by multiple policies in several countries reducing reliance on foreign natural gas, providing tax credits for new anaerobic digestion facilities, extending alternative fuel standards and diverting food waste from landfills. As the anaerobic digestion (AD) industry scales as a result, innovative solutions that easily integrate with existing AD will scale as well. Technologies that optimize AD systems by reducing contaminants, monitoring conditions, and streamlining the upgrading process to increase biomethane yield, will be well positioned for growth to support AD operators looking to meet increasing demands for biomethane. Similarly, for those looking to reduce costs and energy consumption on the industrial side, innovative technologies in waste heat recapture can improve energy recovery systems. 

Anaerobic Digestion and Biomethane Production

The RePowerEU Plan, announced after Russia’s invasion of Ukraine, aims to increase the production of biomethane to 35 billion cubic meters (bcm) from the current rate of 3 bcm that is currently being produced in the EU. Similarly, the US has made commitments to reduce natural gas imports and the Inflation Reduction Act will further incentivize biomethane production and the development of anaerobic digestion facilities through the distribution of tax credits and grants.

AD plays a crucial role in biomethane production. AD processes take organic matter such as manure, sewage, agricultural waste, and food waste, and breaks these substances down to produce biogas which is composed of methane (60%) and carbon dioxide (40%). Biogas can be used to generate heat and electricity directly or be upgraded to produce biomethane, bio-CNG (compressed natural gas) or hydrogen through methane pyrolysis. Multiple companies and operators of AD processes are expected to expand and have received investments to develop projects across the US and EU to meet biomethane demands and to support food waste diversion efforts by reducing the amount of methane released when organic waste degrades in landfills. 

Methane poses a greater climate risk than carbon dioxide with a global warming potential 86 times greater than carbon dioxide over a 20-year time frame and anerobic digestion has the potential to abate 10-13% of current global GHG emissions (3,290 – 4,360 Mt of CO2eq). To meet the demand for biogas and biomethane from various sectors including transportation and oil and gas, companies are supporting the development of AD projects and partnering with dairy providers to reduce their methane emissions from manure. Innovative technologies that will share tailwinds with the growing AD industry include monitoring and modelling technologies, solutions that remove contaminants, and biogas upgrading technologies.

  • AD processes require controlled conditions to produce optimal outputs. Real time monitoring technologies like those provided by BioEnTech allow digestate and internal conditions to be closely monitored using sensors and microlabs. Anessa utilizes modelling software allowing developers to plan operations and test out variables such as tipping fees, transportation costs, feedstock and energy prices to verify viability of projects before construction. 
  • Increasing food waste diversion policies and growing volumes of food waste will require additional depackaging pretreatment services, solutions that remove plastics, metals, and packaging waste, from food waste in preparation for input into AD systems. Traditional depackaging techniques like hammer mill systems can sometimes reduce plastics and metals into smaller particulates which can then be transferred to the AD system and digestate. If the digestate will have agricultural uses, better depackaging techniques like the water based wet pulping systems provided by Gemidan will remove microplastics (including associated PFAS chemicals) and extract 95% of useful feedstock for use in the AD systems. 
  • Various biogas upgrading systems will be used to diversify the outputs of biogas and improve output yields to increase the revenue generated from the systems. For example, Kore Infrastructure is partnering with SoCalGas to create biomethane and carbon neutral hydrogen through methane pyrolysis for use as transportation fuels. Technologies like those provided by Bright Biomethane and Vertus Energy allow for easy integration into incumbent AD systems and increase biogas yield while also reducing energy consumption used in the process.  

These technologies will have multiple opportunities for growth and AD incumbents have plans to expand in North America and Europe. BioEnergy Devco will use the capital gained from a $100 million funding round to expand projects in North America and Blackrock’s acquisition of Vanguard Renewables will provide Vanguard with the resources to meet their goal of having 100 digesters operational by the end of 2026. Policies in the US and the EU, along with voluntary corporate commitments to use renewable energy and fuel sources, are driving strong growth and investments in the AD sector. 


Waste Heat Recovery

Estimates suggest that 20 – 50% the energy used in in industrial processes is lost into the atmosphere or in cooling systems that are unable to recapture the energy. For Switzerland, the total amount of recoverable energy is estimated to be 14PJ per year. Waste heat generated from various industrial processes can be captured and reused, either within the same process, on the same site, or by another company and market. Enhancing heat transfer and optimizing system performance is cheaper than building new systems, and can provide substantial cost and energy savings. 

Medium to high temperature waste heat (greater than 260°C / 500 °F) are the most feasible sources of power generation. Innovative technologies utilizing organic Rankine cycles (ORC) allow for lower heat waste energy to be utilized to generate electricity at lower levels. Exhaust heat, flue gas from burners and boilers are often heat sources for recovery systems. Each industrial system releasing waste heat has specific technical challenges that commercial technologies will have to address. Some of these challenges include securing waste from dispersed sources, capturing lower temperature heat, seasonal waste emission fluctuations, chemical contaminants in waste heat and space limitations for recovery equipment. 

Incumbent solutions capturing waste heat often use Steam Rankine Cycle (SRC) processes, a system that generates steam from waste heat, and Kalina Cycle technology, which uses water and ammonia to generate more efficient energy extractions. Innovations in waste heat technology can augment these systems to improve industrial processes. 

  • Flare gas from oil and gas processes offers a source of waste heat that companies like Swedish Sterling and Echogen recapture. Swedish Sterling’s containerized PWR Block Technology received debt financing in early 2022 and will be used for a large commercial project in South Africa to recapture waste heat from flare gases. 
  • Innovators are using emerging technologies like Organic Rankine Cycle processes to capture heat from lower temperature sources. Rank produce electricity from low temperature heat in small scale operations like they did with their project with Keros Ceramic to capture waste heat that was 165°C (329 °F) to produce up to 20kWe. 
  • Industrial processes that are energy intensive like steel manufacturing benefit from innovations that capture waste from reheating furnaces and annealing lines to generate electricity and support production goals. Climeon was able to partner with SSAB, a steel manufacturer, to provide these services. 
  • Software and Energy as a Service solutions like Skyven Technologies de-risk capital intensive projects using AI and IOT platforms to process real time data and support carbon accounting and risk management services to identify ways to reduce emissions.

Europe is the largest supplier of waste heat-to-power systems, driven by emission regulations and commitments to reduce energy consumption while China is the fastest growing for these technologies driven by industrialization and their need to reduce costs. Waste heat recovery innovations allow for companies managing industrial processes to operate more efficiently and reduce energy consumption and costs without reconstructing entirely new systems. 

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