Biogas, Untapped Transportation Fuel from Waste?

Biogas, Untapped Transportation Fuel from Waste?

In 2018, “What a Waste 2.0” the Urban Development Series produced by the World Bank gave a snapshot of global solid waste management until 2050.

Organic waste comprised 56% of the total waste composition for low income countries, from an annual total waste volume of 93MT per year (million tonnes) or 5% of global waste generated. However, high income countries produced 32% organic waste, from an annual total waste volume of 683MT per year or 34% of global waste generated. 

In 2016, the total global waste volume was 2.01 billion tonnes. By 2050 they project this volume will rise to 3.4 billion tonnes.

Waste Generation by Income Level
Waste Generation by Income Level. Source: Kaza et al. - 2018 | What a Waste 2.0
waste composition
Global waste composition. Source: Kaza et al. - 2018 | What a Waste 2.0
Global Waste Treatment and Disposal percent
Global Waste Treatment and Disposal percent. Source: Kaza et al. - 2018 | What a Waste 2.0

Energy from Organic Waste

All organic waste from food, sewage, manure and gardens naturally decompose without air, via anaerobic bacteria. This process is known as anaerobic digestion (AD). We see AD in peat bogs and the stomach of ruminant animals. This natural process breaks down organic matter to produce biogas and a high-quality organic digestate (fertiliser).

The application of the waste hierarchy summaries the following for organic wastes:-

  1. AD is environmentally better than composting and other recovery options for food.
  2. For garden waste, dry AD followed by post-digestion composting is environmentally better than composting alone.
  3. Energy recovery is a better option for low-grade wood than recycling.

 

Biogas to Biomethane

Transportation fuel Biogas
Biogas Cycle. Diagram: Mildred Williams | Viable AlternativEnergy.com

Biogas primarily comprises methane (50-70%) and carbon dioxide (25-45%). Other components of biogas include hydrogen sulphide, ammonia, and nitrogen. The biochemical composition and yield of the biogas produced from AD depend on the feedstock.

Biogas bacteria thrive in temperatures above 18°C. We see biogas as a fuel source for domestic cooking and lighting across the globe, especially in places with warm climate (average 20-35°C). However, to upgrade biogas it undergoes condensation, particulate removal, compression, cooling and drying to produce biomethane. Biomethane is natural gas grade biogas. Biomethane is at least 90% methane. This fuel is a cleaner and less corrosive, therefore, ideal for engines and gas grids.

In Sweden, Switzerland and Germany they inject biomethane into the natural gas grid. There are strict standards in place limiting the sulphur, oxygen, particles and water dew point, to avoid contamination of the gas grid or the end-users’ heating appliance.

Transportation Fuel Solution?

In our article “The Costa Rica Renewable Approach” we discussed how Costa Rica fulfils 98% of its electricity generation from renewable sources. However, Costa Rica could not generate renewable energy for its transportation and heating needs. Biogas is a viable alternative that can be made in the country to produce sufficient fuel to improve Costa Rica’s environmental goals and public transportation needs. Linköping and Växjö in Sweden are brilliant case studies for municipalities, where biogas is used to produce transportation fuel.

Sources: FNR (2016); Hoornweg (2012)
The ranges of different biofuels. Source IRENA (2018), Biogas for road vehicles. Image: FNR (2016); Hoornweg (2012).

Challenges of Biomethane as a Transportation Fuel

◊Methane is a major contributor to global warming. However, biogas is carbon neutral because the carbon source is plant derived and therefore fixed from atmospheric CO2.
◊Driving long distance with a biomethane engined vehicle is not currently possible due to gas infrastructure. This infrastructure includes gas grid, gas filling stations, and retrofitting biomethane fleet.
◊Crops grown for fuel feedstock take away agricultural land from food production.
◊Driver bias. Changing people’s minds is a major hurdle.
◊Alternative options are available (e.g. electric cars, liquid biofuels).
◊Gas safety procedures and equipment maintenance standards are higher than those required at a standard fill-in station (but not unachievable).

 

Advantages of Biomethane as a Transportation Fuel

♦Overall, biomethane engined vehicles give off less GHG (greenhouse gas), particulates, NOx and noise emissions when compared to petrol and diesel engined vehicles. Biomethane has fewer emissions of carbon monoxide and NOx respectively compared to petrol engined vehicles. When compared to diesel engined vehicles, biomethane is more favourable for NOx and particulates emissions.
♦Processing organic waste via AD saves our groundwater from contamination.
♦Open dumps cause air pollution due to spontaneous combustion of pockets of methane in unregulated sites. Managing the methane produced from organic matter decomposition relieves this problem.
♦Alleviates the contribution of organic waste in rivers and waterways, promoting eutrophication and algal bloom because of lack of oxygen in waterways.
♦Every country in the world has the potential to produce biogas from its own municipal/industrial wastes.
♦Biogas is usually cheaper than other vehicle fuels.

What the Future Holds...

We are not advocating for feedstocks that compete for agricultural land.

Biogas eliminates emissions from waste disposal and manure storage. Additionally, AD and biogas upgrading plants are less costly compared to energy recovery plants.

Public health and the environment are both significantly affected by uncollected or poorly disposed of waste. Improper management of food waste contributes to approximately 5% of global GHG emissions. Developing and maintaining even simple waste management systems improves long-term economic and environmental recovery. These basic improvements can reduce GHG emissions by 25% or more.

We understand that biomethane is not a one size fits all solution. However, if this fuel recovered from sewage and food waste is used for public transportation, we could considerably reduce the overall emissions compared to petrol and diesel engined vehicles.

In conclusion, what we are advocating is for local authorities and municipalities to factor in energy from food waste projects in their future waste processing plans. Thus, ensuring that developing and flourishing societies are well equipped with sufficient premises to process organic wastes via AD plants. Furthermore, eradicating open dumpsites littered with organic waste.

 

The video above shows how Växjö Municipality in Sweden uses biogas for transportation.

Feature Image:

Transportation fuel Biogas
Biogas Cycle. Diagram: Mildred Williams | Viable AlternativEnergy.com

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