How Can We Decrease Waste?

How biochar and polyethylene film recycling can transform the industy

In the face of escalating environmental challenges, the horticulture and greenhouse industries increasingly seek to mitigate their environmental footprint. In this edition, we will look at two prominent areas of innovation: the valorization of biomass waste to produce biochar and the recycling of polyethylene film, a common material in greenhouse operations.

These technologies address waste management issues and contribute to the creation of sustainable products and practices. This newsletter explores the current trends and innovations in these fields, highlighting the potential of biochar production from greenhouse waste and the advancements in polyethylene film recycling, including the novel use of fungi to degrade plastic waste.

Special thanks to Jean Riondel, president of Mini Green Power for his valuable input. 

A DEEPER LOOK
Biomass Valorization: Turning Greenhouse Waste into Biochar

Biomass valorization involves converting organic waste into valuable products such as biochar, biofuels, and biochemicals. This process is particularly relevant for the horticulture and greenhouse industries, which generate significant plant waste.

The Process and Benefits of Biochar Production

Biochar is a carbon-rich material produced by pyrolysis, a thermochemical process that decomposes organic material at high temperatures without oxygen.

The characteristics of the biochar(s) depend on the type of biomass used and the operating conditions during the pyrolysis (temperature, residence time). The UC Davis Biochar Database provides valuable additional information on biochar based on those variables.

The production of biochar from greenhouse waste offers several environmental benefits:

  1. Soil Enhancement: Biochar improves soil health and substrate by increasing its nutrient retention capacity, enhancing microbial activity, and improving water retention. This leads to better plant growth and higher crop yields.

  2. Carbon Sequestration: By converting organic waste into biochar, carbon is locked into a stable form that can remain in the soil for hundreds to thousands of years, thereby reducing greenhouse gas emissions

  3. Waste Reduction: Utilizing greenhouse waste for biochar production helps manage organic waste more effectively, reduces the burden on landfills, and minimizes methane emissions from decomposing organic matter.

The porous structure of biochar (Thies et al., 2009)

Part of biochar's agronomic properties can be explained by the presence of numerous pores in its car structure. Variability in pore size and specific surface area allow plants to retain more (usable) water, oxygenates substrates, and increases interactions with microorganisms.

A CASE STUDY
How It Can Be Leveraged: A Case With Mini Green Power

Jean Riondel, president of Mini Green Power, explains that one of the major advantages of biochar production is that it transforms waste that would otherwise be landfilled or burnt into a useful product. By sequestering carbon in the soil, biochar helps reduce greenhouse gas emissions.

When used in agriculture, biochar speeds up production: it sells for between €1,000 and €1,500/ton, depending on the country in which it is purchased. It also generates increased income as yields rise.

However, there are also obstacles to fully integrating biochar into greenhouse operations. Firstly, you need to be able to secure the supply of biochar and ensure that we qualify the best biochar for the target crop. There are as many types of biochar(s) as biomass wastes and pyrolysis processes. You must ensure that the biochar is contaminant-free (upstream quality control). Moreover, to be able to sell carbon credits, you need to get in touch with specialists to ensure you're well looked after.

For instance, GECA Environnement is a leading North American consulting firm specializing in biochar and pyrolysis, with a global presence. They can support you to access biochar-based carbon credits.

Jean Riondel reports several case studies and examples of companies successfully adopting biochar in their greenhouses. Here are a few notable examples:

  • Circle Organics (Ontario, Canada): Adding biochar improved water retention, reduced dependence on chemical fertilizers, and increased plant resistance to disease. The crops saw an overall improvement in plant health and increased yields.

  • Great Northern Greenhouse (Alaska, USA): In addition to improving yields, the use of biochar has contributed to carbon sequestration, which is beneficial for the environment.

More and more companies are investigating this avenue and commercializing biochar-based products for greenhouse growers.

CHALLENGES
Challenges of Waste Management in the Greenhouse Industry

The greenhouse industry faces significant challenges with waste management, generating substantial organic and plastic waste. Organic waste, including plant residues and trimmings, often ends up in landfills, contributing to greenhouse gas emissions. Plastic waste, primarily from polyethylene films used in greenhouses, poses severe environmental risks due to its non-biodegradable nature. Greenhouse tomato production in Quebec alone generates 42,000 tonnes of waste per year, which is rising yearly (Radio-Canada, 2024).

In the Canadian Province, four companies (GenV, Les Serres Royales, Production Horticole Demers, and Excel-Serres) are working with expert groups to add value to greenhouse residues. The IRDA’s researchers grind greenhouse residues, including small plastic waste, creating homogenous biomass before pyrolyzing them. The aim is to generate value from these residues to generate a financial return for the producer.

This example shows that innovative valorization methods offer promising solutions. Biomass waste can be converted into biochar, enhancing soil health and sequestering carbon. Moreover, some of the waste can also be recycled into energy or other applications, such as bio-oils as biopesticides.

Another important part of the waste is polyethylene films. Indeed, it can be recycled or biologically degraded using fungi. These approaches not only mitigate waste but also create valuable by-products, promoting sustainability in the greenhouse industry.

TACKLING PLASTIC WASTE
Polyethylene Film Recycling: Tackling Plastic Waste in Greenhouses

Polyethylene (PE) film is widely used in greenhouses for its durability and light transmission properties. However, its disposal poses significant environmental challenges due to its non-biodegradable nature. On average, polyethylene plastic film that covers greenhouses has to be changed every 3-5 years, so this represents significant quantities on a global scale. Recycling polyethylene film is therefore essential for sustainable greenhouse operations.

Traditional Recycling Methods

Traditional methods of recycling polyethylene film involve mechanical recycling, where the plastic is cleaned, shredded, and melted to form new products. While effective, this process can be energy-intensive and may not eliminate the environmental impact of plastic waste.

Some greenhouse growers also reuse it in the field as a soil cover, but this use remains limited and the use of polyethylene is not often the most appropriate.

Turn polyethylene films into a valuable resource

Research indicates that pyrolysis of polyethylene films can yield high-quality fuels and chemicals. For instance, studies have shown that the pyrolysis process can effectively convert waste agricultural films into hydrocarbon-rich oils, which can be further refined into fuels or chemical feedstocks. 

Moreover, the conversion of greenhouse plastic waste through pyrolysis not only addresses waste management challenges but also contributes to the circular economy by creating valuable materials from waste. This approach can reduce reliance on fossil fuels, mitigate greenhouse gas emissions, and promote sustainable agricultural practices. The development of efficient pyrolysis technologies could play a crucial role in transforming the greenhouse industry’s plastic waste into a resource, fostering innovation and sustainability within the sector

Emerging Innovations: Fungi-Based Degradation

A groundbreaking development in polyethylene film recycling could be the use of fungi to degrade plastic waste. Certain fungi have been found to possess enzymes capable of breaking down polyethylene, offering a biological solution to plastic pollution.

Fungi such as Aspergillus tubingensis can secrete enzymes that degrade polyethylene into smaller molecules, which are then further broken down into carbon dioxide and water. This process is significantly faster than natural degradation, which can take hundreds of years.

Furthermore, a recent study has shown that Parengyodontium album, a marine fungus, is s capable of mineralizing UV-treated polyethylene (PE) into CO2 (A. Vaskmaa and al., 2024).

The horticulture and greenhouse industries are at the forefront of adopting green technologies to address environmental challenges. The valorization of biomass waste to produce biochar and the recycling of polyethylene film using innovative methods such as fungi-based degradation represent significant strides toward sustainability. These technologies not only help in managing waste more effectively but also contribute to the creation of valuable products that enhance soil health and reduce reliance on fossil fuels.

Complementary Sources

Biochar as a replacement for perlite in greenhouse soilless substrates (Iowa State university, 2013)

Potential use of biochar in horticulture and urban agriculture (Horti-Generation, 2019)

What are biochar carbon credits? (Geca Environment)

Radio-Canada, Les résidus des serres, une ressource qui ne demande qu’à être exploitée (video in French) | La semaine verte, 2024

Valorization of Waste Agricultural Polyethylene Film by Sequential Pyrolysis and Catalytic Reforming (Miguel and al., 2009)