The CIRKULÆR model – A national and regional static flow model of agricultural production, environmental and climatic impacts

Abstract

CONTEXT

Intensive agriculture is a complex, partially industrial and partially circular system that stretches outside the boundaries of fields, herds, and farms. Increasing circularity in agriculture for both environmental and economic reasons requires ex-ante assessment tools designed to operate at the same scale and level of complexity.

OBJECTIVE

To address this, we developed the CIRKULÆR model, which evaluates system-wide climate and environmental effects of changing agricultural practices at a highly interconnected regional scale.

METHODS

The model estimates inputs, outputs, emissions and the flow of biomass, C, N, P, K and energy from crop cultivation and animal production to storage and processing of biomass. We demonstrate the capabilities of CIRKULÆR in a case study based in Denmark, which explored the substitution of cereals with protein crops followed by different storage and utilization steps. We considered twelve scenarios, each involving one of four protein crops (grass-clover, organic grass-clover, alfalfa and faba beans) in one of three soil types (coarse sand, irrigated sand and clay).

RESULTS AND CONCLUSIONS

The greatest differences from business-as-usual baseline were seen in grass-clover, organic grass clover and alfalfa scenarios. Here, biomass processing led to reduced soya imports and increased biogas production, an increase in direct and indirect farm-related GHG emissions and a considerable increase in soil carbon sequestration which, combined, resulted in a decrease in net farm-related GHG emissions. Finally, out-of-farm GHG emissions increased for grass-clover, while a reduction in alfalfa and faba bean was driven by lower N fertilizer imports.

SIGNIFICANCE

These findings represent valuable insights for planning future incentives and policies in agriculture. In addition, the wide range of scenarios that can be evaluated by the CIRKULÆR model underpin the potential of the model to support decision makers.