Introduction
In the quest for low carbon energy sources, understanding the differences between natural (aka: fossil) gas and biogas is crucial. This article aims to demystify these two important energy sources, highlighting how they differ in production, composition, and especially in their impact on greenhouse gas emissions. By exploring these aspects, we can appreciate the unique roles each plays in our energy landscape and the potential for the latter to lead us to a greener future.
Understanding Natural Gas
Origin and Characteristics of Natural Gas
Natural gas is a fossil fuel, formed over millions of years from the decay of organic matter within the earth’s crust (the ‘lithosphere’). It primarily consists of methane and is extracted through drilling, and is a common by-product of coal mining also, whereby disruption of a seam can also unlock pockets of gas. Natural gas is a critical energy source worldwide, used for heating, cooking, electricity generation, and as fuel for vehicles and ships. Its widespread use is attributed to its efficiency and relatively cleaner-burning properties compared to other fossil fuels.
Carbon Emissions from Natural Gas
Although natural gas is cleaner-burning than coal and oil, it still contributes to carbon emissions. When burned, natural gas releases carbon dioxide (CO2), a greenhouse gas, into the atmosphere. Moreover, methane, a primary component of natural gas, can leak during extraction and transportation. Methane is a potent greenhouse gas, with a much higher impact on global warming than CO2 in the short term.
Exploring Biogas
Production and Composition of Biogas
Biogas is a renewable energy resource produced through the anaerobic digestion of organic materials such as agricultural waste, sewage, animal manure and food scraps. This process involves microorganisms breaking down organic matter in the absence of oxygen, resulting in a mixture of gases, primarily methane and carbon dioxide, similar to natural gas. The renewable nature of the source makes biogas a significant player in the clean energy landscape.
Why Biogas Has Lower Carbon Emissions
The key factor distinguishing biogas from natural gas in terms of its greenhouse gas emissions profile is its lifecycle, and the underlying origin of the carbon molecule. During photosynthesis, carbon taken from the atmosphere is fixed using only sunlight and water, to form carbohydrate. The carbon dioxide released when biogas is combusted is roughly equivalent to the CO2 absorbed by the organic matter during its growth, thereby creating a near ‘carbon-neutral’ cycle. Additionally, capturing methane from organic waste through biogas production in a managed system prevents this potent greenhouse gas from being released as fugitive gas directly into the atmosphere, further mitigating climate change impact, at the same time as it is effectively displacing natural gas consumption in the economy.
The Key Differences Between Biogas and Natural Gas
Source and Sustainability
The most significant difference between biogas and natural gas lies in their sources. Natural gas is a non-renewable resource, formed over millions of years, and its reserves are finite. The carbon locked in this gas has been slowly taken out of circulation in the biosphere, and no longer takes any part in the biogenic carbon cycle, therefore makes no contribution to the ‘greenhouse effect’. In contrast, biogas is renewable, produced from organic waste materials that are continuously replenished. This fundamental difference highlights biogas’s potential role in contributing to decarbonisation of the economy.
Environmental Impact
Another critical difference is the environmental impact of each. The extraction and burning of natural gas contribute to greenhouse gas emissions, despite being cleaner burning than other fossil fuels. On the other hand, biogas production and utilisation significantly reduces environmental impact by recycling waste and releasing fewer emissions during its production cycle, delivering emissions reductions in excess of 90% on a life cycle basis.
Economic Considerations
Economically, natural gas has been a cornerstone in the energy market for decades due to its abundance and established infrastructure. Biogas, while growing in popularity, faces challenges in terms of production scale and initial investment in Australia. However, its potential to reduce waste management costs and produce renewable energy is clear. This solution is well demonstrated in many countries around the world, where it is a material and legitimate part of the renewable energy mix, and provides a pathway to delivering emissions reductions for a range of ‘hard to abate’ industries and applications.
Carbon Emissions: Natural Gas vs. Biogas
Natural Gas Emissions
When natural gas is burned, it releases carbon dioxide, a greenhouse gas. Additionally, its extraction and distribution can result in methane leaks. Methane is over 25 times more potent as a greenhouse gas than CO2 over a 100-year period, making its management crucial in climate change mitigation.
Biogas and Carbon Neutrality
Biogas stands out for its lower carbon footprint, using technology and infrastructure that is ready to deploy and is competitive in today’s market. The CO2 released when combusting biogas is offset by the CO2 absorbed by the biomass from which it was produced. This cycle can be close to carbon-neutral and even carbon negative when ‘value-adding’ to the biogenic CO2 fraction is undertaken, especially when considering biomethane captured from organic waste, which otherwise would have been released into the atmosphere.
Conclusion
In summary, understanding the differences between biogas and natural gas is key to appreciating their roles in our current and future energy landscapes. While natural gas has been a significant energy source for decades, its environmental impact cannot be overlooked. Biogas, on the other hand, offers a low emissions and Circular Economy-oriented alternative, by recycling biogenic carbon and managing otherwise fugitive emissions from discarded or surplus organic waste. The transition from traditional fossil gas to renewable biogas is not just technically and commercially feasible but also a step towards a positive regeneration of our rural industries and communities. As we continue to seek solutions for a greener planet, this solution becomes increasingly important in our journey towards sustainability, providing both energy resilience and diversity.
