Solar-Powered Hydrothermal Carbonization for Food Waste Management and Biochar Production

Fereshteh Mostafavi Meresht¹ , Eslam Mostafavi Maresht²

1. PhD student at Department of Communication and Internet, Istanbul Commerce University
2. PhD student at Department of Geological Engineering, Istanbul University – Cerrahpasa, Istanbul

 

Introduction

The global challenges of food waste and energy consumption are growing at an alarming rate. As urban populations increase and food demand rises, the amount of food waste generated each year is also climbing currently, it’s estimated that around 1.3 billion tons of food is wasted globally (Prasad et al., 2020). In addition to the social and economic costs, food waste contributes significantly to environmental issues. When food is discarded and incinerated, it releases greenhouse gases like carbon dioxide and methane, which account for nearly 26% of total global emissions (Funke & Ziegler, 2010).

On the other hand, much of the energy used in today’s systems still comes from non-renewable sources like coal and oil, contributing to resource depletion and environmental degradation (Choudhury et al., 2021). In response to these challenges, there is an urgent need to find sustainable solutions that can address both food waste and energy consumption. This project proposes a solution that could transform food waste into a valuable resource: solar-powered hydrothermal carbonization (HTC). By combining waste management with clean energy technology, we can reduce greenhouse gas emissions, lower energy consumption, and create valuable products like biochar.

Problem Statement

Food waste is an escalating global problem, with the restaurant industry and households contributing significantly to the 1.3 billion tons of food waste generated annually (Prasad et al., 2020). This waste is often disposed of by incineration, contributing to pollution and climate change. At the same time, energy production is heavily reliant on non-renewable sources, which are both finite and environmentally harmful. As a result, addressing these interconnected issues requires innovative solutions that can both manage waste and reduce reliance on fossil fuels.

Project Objective

This project aims to develop an energy-efficient, sustainable process for converting food waste into biochar using solar-powered hydrothermal carbonization (HTC). By integrating solar energy into the HTC process, we hope to reduce the environmental footprint of food waste disposal, provide a renewable energy source, and contribute to carbon sequestration efforts. The objectives are as follows:

1. Convert food waste into biochar: Using HTC to transform organic waste into biochar, a stable form of carbon that can be used for energy production or soil improvement (Lehmann & Joseph, 2015).
2. Integrate solar energy: Use solar power to fuel the HTC process, reducing the need for non-renewable energy sources (Kalogirou, 2014).
3. Reduce greenhouse gas emissions: By diverting food waste from incineration and converting it into biochar, the project will help reduce the release of harmful gases like carbon dioxide and methane (Choudhury et al., 2021).
4. Promote circular economy practices: Turn food waste into valuable resources, contributing to a more sustainable and resource-efficient food system (Lehmann & Joseph, 2015).

Literature Review

As the global population grows, so does the demand for food. However, food production and consumption also lead to an increasing amount of waste. Around 30% of food produced worldwide is wasted annually, much of it ending up in landfills or being incinerated (Kwapinska et al., 2019). The environmental consequences are significant, as food waste accounts for a large portion of greenhouse gas emissions (Funke & Ziegler, 2010). Given that this waste is organic, it offers potential as a resource, particularly in the form of biofuels and biochar. Biochar is a stable, carbon-rich material that can be used in energy production or as a soil amendment, where it can improve soil quality and sequester carbon (Lehmann & Joseph, 2015).

Hydrothermal carbonization (HTC) is an effective technology for converting wet biomass, like food waste, into biochar. By applying heat and pressure in the presence of water, HTC can break down organic matter into biochar, bio-oil, and gases—products that can be used for energy generation (Funke & Ziegler, 2010). However, the process requires significant energy input, traditionally derived from fossil fuels. To make HTC more sustainable, integrating solar energy into the process is a promising solution. Solar thermal systems can provide the necessary heat for HTC, reducing the reliance on non-renewable energy sources (Müller et al., 2018).

Previous research has shown that HTC can successfully convert food waste into biochar, and the process is particularly effective with wet waste, which is common in the restaurant industry (Kwapinska et al., 2019). This project aims to build on these findings by integrating solar power into the HTC system, reducing costs and environmental impacts.

Methodology

The pilot model for producing biochar from food waste used a straightforward yet effective process. The setup involved using an autoclave, capable of holding 1 kg of food waste, combined with a furnace to heat it. This initial experiment relied on electricity to heat the system to 220°C, maintaining this temperature for 4 hours.

The process began by preparing the food waste—gathering, chopping, and mixing it to ensure an even composition. To create the ideal conditions for hydrothermal carbonization (HTC), 5 liters of water were added to the 1 kg of wet food waste. This water addition simulated the high-pressure environment necessary for HTC, akin to natural coal formation deep underground. The mixture was then sealed in the autoclave.

Heating took place in a furnace pre-set to 220°C. For 4 hours, the heat allowed the water to act as a catalyst, breaking down the food waste at a molecular level. This process transformed the waste into a dense, carbon-rich material: biochar. After cooling, the mixture was carefully removed from the autoclave. The solid biochar was separated and dried to remove any leftover moisture. The end result was a coal-like powder, yielding about 10% of the initial weight of the waste, a typical result for food waste processed through HTC.

This pilot project demonstrated that biochar could be efficiently produced from food waste using conventional heating. However, relying on electricity raised questions about sustainability. Looking ahead, the main goal is to replace the electrical power source with solar energy. Using solar thermal collectors to reach the necessary 220°C temperature would reduce both costs and environmental impact. This shift to renewable energy would make the entire process more sustainable, serving as a model for eco-friendly waste management and biochar production.

To achieve the project’s objectives, we will undertake the following steps:

1. Collection of food waste: We will gather organic food waste from local restaurants and households. The waste will be prepared by removing non-organic materials.
2. Solar-Powered Hydrothermal Carbonization (HTC):
   • Setup: We will use solar thermal collectors to heat water, which will be used in the HTC process. The food waste will be placed in a high-pressure vessel where it will undergo hydrothermal carbonization.
   • Process Optimization: Based on previous research (Prasad et al., 2020), we will experiment with varying temperatures (180–250°C) and pressures (5–25 MPa) to determine the optimal conditions for biochar production.
   • Energy Efficiency: By using solar energy, we aim to reduce the overall energy consumption of the HTC process, making it more sustainable and cost-effective (Kalogirou, 2014).
3. Product Analysis: The output from the HTC process will include biochar, bio-oil, and gases. These will be analyzed for their energy content and potential uses.
   • Biochar will be tested for its carbon content, stability, and suitability for energy generation or soil improvement (Lehmann & Joseph, 2015).
   • Bio-oil and gases will be assessed for their potential as alternative energy sources.
4. Environmental Impact Assessment: A life-cycle analysis (LCA) will be conducted to compare the environmental impact of our solar-powered HTC process with traditional waste disposal methods, such as incineration or landfill disposal (Choudhury et al., 2021).

Expected Outcomes

This project is expected to achieve several key outcomes:

1. Sustainable waste management: By converting food waste into biochar, we can reduce the amount of waste that ends up in landfills or is incinerated, helping to mitigate greenhouse gas emissions.
2. Energy production: The biochar, bio-oil, and gases produced during HTC can be used for energy generation, reducing reliance on non-renewable energy sources.
3. Cost savings: Using solar energy to power the HTC process will reduce operational costs and make the process more economically viable in the long term (Müller et al., 2018).
4. Environmental benefits: The use of biochar as a soil amendment and carbon sequestration tool can help mitigate climate change by capturing carbon from the atmosphere (Lehmann & Joseph, 2015).

Novelty of the Project

The novelty of this project lies in its innovative approach to addressing two pressing global challenges—food waste and energy consumption—by combining solar energy with hydrothermal carbonization (HTC). While HTC is a well-established technology for converting organic waste into biochar, our project distinguishes itself by integrating solar power to fuel the HTC process. This integration not only enhances the sustainability of the process but also makes it more cost-effective and environmentally friendly by reducing reliance on fossil fuels.

Furthermore, food waste is often considered a troublesome byproduct of the global food system, but we are reimagining it as a valuable resource. By converting food waste into biochar, we can both sequester carbon and produce an alternative energy source. The use of solar energy reduces the carbon footprint of the entire process, making it a triple-win solution: addressing food waste, providing renewable energy, and reducing harmful emissions.

Another unique aspect is the project’s potential for scalability. While this is a pilot project, the model can be adapted for various scales, from small-scale applications in restaurants to larger commercial systems, making the solution flexible and adaptable to different needs and regions. By proving the concept with this initial phase, the project could serve as a blueprint for a global shift toward more sustainable waste-to-energy systems.

Budget

The budget for this project has been carefully planned to ensure that resources are allocated effectively, focusing on the core components necessary for its successful execution. Below is a summary of the key budget categories:

Category	Estimated Cost (USD)	Description
Solar Energy Equipment	$90,000	Purchase and installation of solar panels, thermal collectors, and associated infrastructure to harness solar energy for HTC.
Hydrothermal Carbonization Unit	$100,000	Cost of high-pressure reactor and associated equipment for the HTC process. Includes both hardware and installation costs.
Food Waste Collection & Processing	$30,000	Collection, transportation, and preparation of food waste (e.g., sorting, removing non-organic materials).
Labor and Personnel	$160,000	Salaries for project team members, including research assistants, technical staff, and project management.
Materials and Consumables	$30,000	Supplies such as chemicals, water, and testing equipment required for the HTC process and product analysis.
Testing and Analysis	$50,000	Laboratory costs for analyzing the biochar, bio-oil, and gases produced by HTC, including energy content and environmental impact assessments.
Land for the project	$1500000	1000 square meters of Land for the project
Miscellaneous	$40,000	Contingency funds for unexpected expenses, transportation, and minor administrative costs.

Total Estimated Budget: $2,000,000

This budget is designed to cover both the hardware and operational costs involved in the pilot project. It reflects our commitment to sustainability while ensuring the project’s feasibility and successful implementation. We also plan to secure additional funding or partnerships as needed, especially as we move toward scaling the technology.

Timeline

A successful timeline is critical for ensuring the project is carried out efficiently and on schedule. Below is a 3-phase timeline for the project’s key milestones:

Phase 1: Preparation and Setup (0–3 Months)

• Objective: Establish the infrastructure needed to carry out the project.
  • Month 1: Finalize project team, acquire permits, and secure contracts with food waste suppliers (local restaurants and households).
  • Month 2: Procure solar panels, HTC unit, and necessary equipment. Begin installation of solar energy infrastructure and HTC reactor.
  • Month 3: Complete the setup of food waste collection systems and test the functionality of the HTC unit. Conduct initial tests to calibrate the process.

Phase 2: Testing and Optimization (4–6 Months)

• Objective: Fine-tune the hydrothermal carbonization process and ensure solar energy integration.
  • Month 4: Start the HTC process using food waste and monitor the temperature and pressure conditions. Experiment with different food waste types (e.g., dairy, vegetables) to determine the most efficient conditions for biochar production.
  • Month 5: Analyze the first batch of biochar, bio-oil, and gases. Test the energy output and environmental impact. Adjust solar power usage based on performance.
  • Month 6: Finalize optimization of the HTC process, ensuring it runs smoothly on solar energy. Begin larger-scale production of biochar for analysis.

Phase 3: Evaluation and Scaling (7–12 Months)

• Objective: Assess the outcomes of the pilot project and evaluate scalability.
  • Month 7: Complete an environmental impact assessment and compare the results with traditional waste disposal methods (incineration, landfill).
  • Month 8–9: Refine the overall system based on test results. Continue biochar production and energy generation.
  • Month 10–11: Compile findings and create a detailed report on the feasibility and scalability of the solar-powered HTC system.
  • Month 12: Present results to stakeholders, finalize recommendations for scaling, and explore future funding opportunities.

By the end of the year, we expect to have fully validated the solar-powered HTC technology, proven its environmental and economic benefits, and laid the groundwork for scaling up the solution to other regions and industries.

Conclusion

Food waste and energy consumption are two of the most pressing environmental challenges we face today. Every year, millions of tons of food are discarded, while at the same time, much of the world’s energy is still drawn from non-renewable sources, leading to significant environmental and economic costs. This project offers a novel and sustainable solution to both of these issues by combining solar-powered hydrothermal carbonization (HTC) with food waste management.

By harnessing the power of the sun to fuel the HTC process, we transform food waste into biochar, a valuable byproduct that not only helps sequester carbon but can also be used as a renewable energy source. This process provides a cost-effective, environmentally friendly way to reduce greenhouse gas emissions, tackle waste, and promote circular economy practices. In doing so, it aligns perfectly with the goals of sustainable development and green energy innovation.

If successful, this project could pave the way for the widespread adoption of sustainable waste-to-energy technologies, particularly within the restaurant industry, which is a major contributor to food waste. By proving that food waste can be converted into useful products like biochar and biofuel, we aim to inspire other industries and communities to adopt similar models, creating a ripple effect that extends far beyond the pilot phase.

Ultimately, our goal is to demonstrate that what is often seen as waste can actually become a valuable resource—one that not only contributes to reducing our environmental footprint but also creates new opportunities for renewable energy production. This project holds the potential to spark a larger movement toward more sustainable waste management and energy practices, driving positive change at both local and global levels.

 

References:

• Choudhury, A., et al. (2021). Sustainable biochar production: Utilizing solar energy in the hydrothermal carbonization process. Renewable and Sustainable Energy Reviews, 134, 110389.
• Funke, A., & Ziegler, F. (2010). Hydrothermal carbonization of biomass: A review of the process and its applications. Bioresource Technology, 101(10), 3359–3368.
• Kalogirou, S. A. (2014). Solar energy applications for heating and cooling of buildings. Energy, 67, 146-156.
• Kwapinska, M., et al. (2019). Conversion of food waste into biochar: A sustainable solution for waste management and carbon sequestration. Waste Management, 95, 92-103.
• Lehmann, J., & Joseph, S. (2015). Biochar for Environmental Management: Science, Technology, and Implementation. Routledge.
• Lu, Y., et al. (2017). Hydrothermal carbonization of food waste for biochar production and its use as an energy source. Journal of Cleaner Production, 162, 631-638.
• Müller, S., et al. (2018). Solar-assisted biomass conversion: Feasibility and environmental benefits. Renewable Energy, 124, 193-201.
• Prasad, M., et al. (2020). Renewable energy solutions for waste management: A review of the potential for solar-powered biomass conversion systems. Renewable and Sustainable Energy Reviews, 120, 109618.