My dilemma: Soy milk or dairy?

Soy milk is made from soy beans which are dried, then soaked in water and finely ground. The resulting drink has roughly the same protein content as milk (about 3.5 per cent), and can be curdled and pressed into tofu in the same way that milk is turned into cheese. Soybean plants are grown both as a food crop and animal feed in regions with hot summers, including the Unites States, South America, China and India. Beans used in New Zealand products are often sourced from Australia.

Cow’s milk in New Zealand is by contrast a local product, though some imported feed is used. Cows graze mostly outdoors with milk collected and processed over a milking season that matches the period of greatest summer grass growth. Only a small percentage of milk produced is consumed in New Zealand; the majority is exported.

Let’s look at the environmental pros and cons of each process.

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Pros

When consumed locally, New Zealand dairy products have minimal ‘food miles’ attached with only local transport, plus some imported feed required.

Pasteurising fresh milk for domestic consumption requires relatively little energy.

Making protein from soy beans is at least 13 times more energy efficient than making it from milk, according to one US study. However this difference is likely to be less pronounced in New Zealand, where farming is less energy-intensive than in the US.

Cons

The dairy industry pollutes waterways at unsustainable levels through faecal run-off, sediment and excess nutrients from cow urine and fertiliser.

Conversion of forestry land to dairying is exacerbating water issues.

Belches and farts from dairy cows contribute substantially to our greenhouse gas emissions. Almost half of New Zealand’s emissions come from agriculture, with dairy cows contributing to rising levels.

Drying milk into powder for export uses a lot of heat, largely from burning ‘dirty’ coal, wood and gas.

The growing demand for soy has been linked to deforestation in South America as land is cleared for plantations. However, soy milk used in New Zealand usually comes from Australian beans, which are sustainably harvested.

Soy products purchased in New Zealand are imported, adding to their ‘food miles’.

Soy milk is a much more processed product than milk, and usually has sugar, calcium, vegetable oil, preservatives and vitamins added, which all have environmental impacts of their own.

Average prices per litre

• Regular dairy milk: $1.50
• Regular soy milk: $2.99
• Organic dairy and soy milk: Both around $3.69

The verdict

Drinking Australian-sourced soy milk is a greener choice than drinking milk. However, you can cut out many of the worst impacts of dairy products by choosing organic milk.