Life-cycle analysis reduces emissions in liquid milk production

To help the US dairy industry achieve its goal of a 25% reduction in greenhouse gas emissions by 2020, University of Arkansas (U of A) researchers have developed a ‘cradle-to-grave’ life-cycle analysis of milk.

The analysis will provide guidance for producers, processors and others in the dairy supply chain and will help these stakeholders reduce their environmental impact while maintaining long-term viability.

An interdisciplinary team of U of A researchers looked at all facets and stages of milk production, from the fertiliser used to grow the animal’s feed through to disposal of packaging waste after consumer use.

The researchers found that for every kilogram of milk consumed in the US per year, 2.05 kg of greenhouse gases, on average, are emitted over the entire supply chain to produce, process and distribute that milk. The largest contributors were feed production, enteric methane (gas emitted by the animal) and manure management.

In identifying areas where impact can be lessened, the researchers focused on farms, where processes for feed production, handling of enteric methane and manure management vary greatly and therefore represent the greatest opportunities for achieving significant reductions.

The researchers suggested widespread nutrient management strategies that link inorganic fertiliser use with the application of manure for crop production. They recommend dry lot and solid storage systems as preferred management strategies, rather than anaerobic lagoons and deep bedding. Methane digesters should be a high priority for larger farm operations, according to Greg Thoma, professor of chemical engineering.

At the processor and distributor level, greater emphasis on truck fleet-fuel usage and consumption of electricity will reduce emissions, the researchers said. Implementing standard energy-efficiency practices focused on refrigeration and compressed air systems, motors and lighting will also lead to reduction. Likewise, processor plant fuel reductions can be achieved through improved steam systems and continued energy-efficiency improvements in other operating practices.

With packaging, emissions reductions could come from improved bottle designs resulting in less material use. Specifically, changing the bottle-cap manufacturing process from injection moulding to thermoforming may lower environmental impact.

Finally, the researchers recommended a careful examination of trucking transport distances to realise greater optimisation and efficiency of routes. They also suggested transport refrigeration systems that use fewer refrigerants.

The research was published as a special issue, ‘Carbon and Water Footprint of US Milk, From Farm to Table’, in the International Dairy Journal in April.