Process & Systems Modelling

Modelling methane production from ruminants

Livestock agriculture is estimated to contribute between 9% and 18% of total anthropogenic greenhouse gas (GHG) emissions. A significant element of such emissions is the production of methane in ruminants, which also represents a loss of energy that might otherwise be available for growth or milk production.

In collaboration with scientists at RINH and SRUC, we have developed a simple process-based model to simulate methane production in ruminants. The model represents two classes of microbes: the fermenters, which grow by consuming ingested feed and produce hydrogen as a by-product; and, the methanogens, which consume the hydrogen producing methane in the process. We obtain the model’s parameter values from the literature and also by using time series data of feed intake and hydrogen and methane production from a group of finishing steers on two different diets. The model captures the dynamics of the system (see figure), demonstrating a level of correlation that can act as a starting point for assessing mitigation strategies for reducing methane emissions from ruminants, e.g. through changes in the composition of feedstocks.

modelled methane productionObserved and modelled methane production from a finishing steer on a concentrate diet. Measurements (solid black line) are taken in a respiration chamber at 6 minute intervals. The model simulation (dashed red line) is driven by the individual steer’s feed intake, but otherwise uses parameter values derived from methane measurements excluding the steer in question.

Further details from: Helen Kettle

Article date 2015

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