Comprehensive Study Notes on Enteric Methane Mitigation and Carbon Accounting in Australian Carbon Carbon Markets

Ruminant Metabolism and Methane Energy Dynamics

• Methane ($CH_{4}$) is a primary byproduct of ruminant digestion, occurring as a result of enteric fermentation in the gut.
• Methane is a high-energy gas containing approximately $55\,MJ\,kg^{-1}$ (megajoules per kilogram), a value very similar to that of natural gas.
• When animals release methane (burping), they are effectively losing a significant portion of their dietary energy, which represents a biological and economic inefficiency.
• Statistics on energy loss due to methane production:
  • Approximately $6\% \text{ to } 6.5\%$ of an animal's gross energy intake ($GEI$).
  • Approximately $10\%, 15\%, \text{ or } 17\%$ of their metabolisable energy ($ME$).
• Historical Context: Research on methane reduction began in the 1960s. Initial interests were strictly from a livestock productivity perspective to minimize energy waste. Modern research has shifted focus toward climate change mitigation, with hundreds of millions of dollars invested in the issue.
• Challenges: It is exceptionally difficult to permanently alter the rumen gut microbe composition.

Enteric Methane Mitigation Strategies and Technologies

• Bovair: A synthetic product that can be used as a supplement for cattle, sheep, and goats to reduce methane output.
• Asparagopsis: A type of seaweed used as a feed supplement.
  • Active Ingredient: Bromoform.
  • Safety Concerns: Bromoform is identified as a carcinogen and is highly volatile.
  • Human Risk: Farmers or individuals administering the supplement face potential health risks due to volatility; it must be administered carefully.
  • Environmental Residue: Currently, published papers suggest there is no residue of bromoform in the final meat or milk products, but companies must evaluate this within their supply chains.
• Genetic and Pasture Research: Ongoing efforts into breeding livestock with lower methane traits and developing pastures with anti-methanogenic properties.
• Oil Supplements: Used as another enteric methane mitigation strategy.
• Implementation Constraints: These supplements are currently most viable in controlled environments with daily feed turnover, such as feedlots or dairies. Applying these in pasture-based systems is far more difficult and remains cost-prohibitive with no reported productivity benefits at this stage.

Greenhouse Gas Accounting: The Scope Framework

• Scope language is used to clarify responsibility, distinguish value chain impacts, and ensure accounting is credible and comparable.
• Scope 1: Direct emissions from sources that are owned or controlled by the entity. For a farm, this includes:
  • Livestock emissions (enteric methane).
  • Emissions from cropping enterprises.
  • Fertilizer application.
  • Machinery and fuel use.
• Scope 2: Indirect emissions from the generation of purchased energy. This is always defined as emissions from grid-supplied electricity.
• Scope 3: Upstream and downstream emissions occurring in the value chain.
  • For a producer, these are emissions occurring before or after the farm.
  • For a retailer (e.g., a supermarket), Scope 3 includes all the emissions from the farms that supply their beef, lamb, or milk.

The Carbon Cycle in Natural vs. Fossil Systems

• Fossil Fuels: The process is linear; carbon is extracted from the ground and released into the atmosphere, contributing directly to the greenhouse effect.
• Natural Systems: Can exist in one of three states: balance, loss, or gain.
  • Balanced System: Seen in well-managed pastures without significant management changes. $CO_{2}$ respired by microbes is returned to the soil.
  • Losing System: Carbon is released from the soil due to significant cultivation, loss of ground cover, or land degradation.
  • Gaining System: Carbon is actively sequestered into the soil through specific management changes.
• Tree Dynamics: Changes in tree carbon are easier to measure visually and via satellite.
  • Balance: Dead older trees are replaced by new growth.
  • Loss: Land clearing results in a significant loss of carbon.
  • Gain: Planting new trees sequestering carbon.
• Livestock Specifics: Livestock systems are unique as they convert $CO_{2}$ into a product (meat/milk) but release methane as a warming byproduct.

Strategies for Emission Reduction on Farms

• Strategy 1: Productivity and Profitability (The "Low-Hanging Fruit"): Improving herd and flock productivity, nitrogen use efficiency, and crop yields.
  • Logic: Producing the same or more beef in a shorter timeframe reduces the animal's lifetime. Fewer days on the property means fewer days the animal is burping methane into the atmosphere.
• Strategy 2: Technological Implementation: Using products like Bovair and Asparagopsis, or installing solar panels.
• Strategy 3: Soil Carbon Sequestration: Storing carbon in the soil. It provides productivity benefits but is notoriously difficult to measure and prove statistically over time.
• Strategy 4: Tree Planting and Revegetation: Easily monitored via satellite and modeling, but often requires taking land away from agricultural production.

The Australian Carbon Credit Unit (ACCU) Scheme

• The ACCU scheme is the most credible system in Australia, encouraging businesses to reduce emissions or store carbon.
• Participants earn one carbon credit for every ton of $CO_{2}$ equivalent ($CO_{2}\text{-}e$) stored or avoided.
• Credits can be sold to the government or on a secondary market.
• Current Market Price: Approximately $\$30$ per ton.
• Method Categories:
  • Savanna burning.
  • Vegetation projects (e.g., Human-Induced Revegetation [HIR], which is now superseded, and Environmental Plantings).
  • Waste.
  • Agricultural methods (Soil carbon, beef herd management, effluent management).
• Project Commitment: Registering a project involves a permanence obligation of either $25$ years or $100$ years.

Challenges in Measuring and Modeling Soil Carbon

• Physical Measurement Limitations: A standard soil core has a diameter of only $40\,mm$. In a large paddock, a single core represents well below $1\%$ of the total soil.
• Statistical Noise: To overcome spatial variation and achieve a statistically significant baseline, a high volume of samples is required.
  • Sampling requirements can range from $100$ to $400$ samples per property.
  • Cost: Sending a team for collection and laboratory analysis for $100$ samples can cost approximately $\$50,000$.
• Modelling: While modeling tools are allowed under some methods, physical sampling for verification is still required.
• Environmental Factors: Soil carbon is highly correlated with rainfall. Gains often appear during good rainfall years, while losses occur during dry periods. This makes finding a long-term financial return difficult, though the productivity of the land may improve regardless of the credit generated.

Strategic Project Management and Succession Planning

• Farmers may register multiple separate projects on a single property rather than one large project for various reasons:
  • Succession Planning: If a farmer intends to split land between heirs (e.g., a son and a daughter), setting up separate projects prevents future legal and management complications across multiple properties.
  • Risk Management: Breaking projects up by management strategy allows a farmer to cancel a failing project without impacting the entire property's carbon status.
• Downside of Multiple Projects: Each project carries heavy monitoring, reporting, and compliance requirements. Duplicating these leads to repetitive and labor-intensive work.

Questions & Discussion

• Question (Kara Tighe): How is the side of things going regarding reports that Sweden lost a large number of dairy cows after feeding methane-reducing products?
• Response (Emma Longworth): I haven't heard about that specific incident. Studies on Bovair and Asparagopsis typically report no significant side effects. However, if products are not well-researched, there are potential risks to animal welfare, meat quality, and residue levels. Bromoform specifically is a concern because it is carcinogenic, though published papers deny residue presence in the final product. Volatility also creates a human health risk during administration.