Achieving a net zero: thinking inside the box

For the farming sector to achieve net zero 10 years before the rest of the economy, it could require some gradual moving of the goalposts. In the short-term, being carbon neutral may be defined simply as what is consumed and produced on-site. Over time, however, as other parts of the economy also reach net zero, the box can be expanded to include other processes, both up and downstream of the site itself.

Inputs and outputs

Heat

• Insulate where possible to reduce heat loss but beware of reducing light transmission.
• Ensure all doors and vents close fully.
• Produce heat from sustainably sourced biomass or heat pumps where the electricity is generated by renewables, such as solar or wind.
• Use waste heat from local industry.

CO₂

• Utilise CO₂ from heat generation where possible, e.g. extract from biomass boiler flue gas.
• Identify local industries producing CO₂ as an unwanted by-product.

Light

• Grow seasonal produce with no need for supplementary lighting.
• Ensure optimum light transmission to maximise sunlight.

Electricity

• Install solar panels, ideally on south-facing rooftops.
• Use solar glass to generate electricity but beware of reduced light transmission. These may also add some additional insulation.

Strategy

• Reduce heating setpoints and accept cooler growing temperatures.
• Create a detailed overview of the growing climate by using an appropriate number of measuring boxes/data sensors.
• Optimise air movement to create a homogeneous climate, ensuring climate is controlled on accurate data.
• Accept higher humidity levels where possible and use a ‘vent then heat’ strategy, reducing the amount of air that needs to be warmed compared to the more conventional ‘heat then vent’ approach.

• Recycle irrigation water, which can reduce fertilizer usage. Use bio-beds or UV treatment with electricity provided by on-site renewables.
• Avoid peat-based substrate and use environmentally sustainable alternatives.

Produce

• Grow hardier varieties more resilient to lower temperatures.
• Make sure cold stores, if used, are well-insulated. Utilise waste heat from chillers.
• Sell produce locally to reduce food miles.
• Use a ‘green’ fleet, such as biodiesel trucks, to deliver produce to markets.

Law of diminishing returns

Example: Take three technologies, each capable of reducing emissions by 20%. By implementing all three, the cumulative saving is 1 – (0.8 x 0.8 x 0.8) = 49%, which is less than the 3 x 20% = 60% some might expect.

Although the end result is the same, regardless of the order you install these hypothetical pieces of technology, it is worth going for the big wins first – i.e. adopt first a solution that will reduce emissions by 50% rather than 10%, to benefit from the greater saving for the longest period of time.

Food for thought

• Is it okay to use waste heat from another industry burning fossil fuels?
• Is CO₂ produced from biomass carbon neutral?
• What transportation emissions need to be accounted for?
• Does how the workforce travels to work count?

What can I do straight away?

• Insulate – keep heat loss to a minimum to reduce your fuel bills.
• Accept lower temperatures and higher humidity à Added value versus additional cost.
• Go ‘green’ – switch from fossil fuels (e.g. gas/oil) to biomass or heat pumps; install solar panels on south-facing roofs.

What should I do next?

• Identify local businesses with waste heat or CO_2.
• Consider growing less energy intensive crops.

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