Organic Waste Diversion: The Carbon Hierarchy Matters

Waste Disposal Hierarchy

In sustainability reporting, many organisations celebrate “diversion from landfill” as a success metric. But from a carbon accounting perspective, not all diversion pathways deliver the same climate benefit.

The waste hierarchy exists because different treatment options retain — or destroy — material value at different stages of the carbon cycle.

When we apply a lifecycle lens to organic waste, the ranking becomes clear:

• Animal Feed (Highest Carbon Benefit)

• Composting (Soil Carbon Recovery)

• Biofuel / Anaerobic Digestion (Energy Recovery)

1. Animal Feed: Maximum Carbon Retention

When suitable organic waste is converted into livestock feed:

• It displaces virgin feed crops (maize, soy)

• Avoids upstream agricultural emissions (Scope 3)

• Reduces land-use pressure

• Preserves embedded carbon in the food chain

From a lifecycle assessment (LCA) perspective, this pathway:

• Avoids both landfill methane

• Avoids agricultural production emissions

This makes it the highest carbon-value recovery option for suitable food-grade waste.

2. Composting: Carbon Sequestration & Soil Health

Composting:

• Prevents methane generation in landfill

• Returns nutrients to soil

• Improves soil organic carbon

• Enhances water retention and climate resilience

While composting does release some CO₂ during decomposition, it supports long-term soil carbon storage and regenerative agriculture systems. It is a strong climate-positive pathway — particularly for non-feed-grade organics.

3. Biofuel: Energy Recovery (But Carbon Conversion)

Anaerobic digestion captures methane and converts it into energy — which is beneficial compared to landfill.

However:

• Nutritional value is destroyed

• Embedded carbon is converted into biogas

• The material leaves the food system permanently

Energy recovery offsets fossil fuel use, but it ranks lower because it converts biological nutrients into short-term energy rather than maintaining carbon in regenerative systems.

Why This Matters for ESG & Scope 3 Reporting

As organisations in the Western Cape increase organic diversion, the question should shift from:

“Are we diverting from landfill?”

to

“Are we selecting the highest carbon-value recovery pathway available?”

The choice of treatment pathway materially impacts carbon outcomes.

Landfill diversion is no longer enough.

Carbon efficiency per tonne is the next metric.

Before selecting a disposal route, ask:

• Can this waste displace virgin agricultural production?

• Can it enhance soil carbon?

• Or are we prematurely converting nutrients into energy?

The waste hierarchy is not just operational - It is carbon strategic.