Slurry – it’s time we ‘mined’ all its nutrients

Much discussion amongst farm stakeholder groups in Northern Ireland over recent days has focussed on the issue of how best to tackle the challenge of minimising ammonia volatilisation levels, while spreading slurry.

Yes, this is all very important – at one level. But, in many ways, it’s a debate that fails to take-in the bigger picture of how to deliver a wholly sustainable farming sector.

In my opinion, the word ‘waste’ should be removed from the lexicon of agriculture.

The fact is that everything produced on our farms has a value. And this is particularly the case where slurry and farmyard manures are concerned.

Both are rich sources of nitrogen, phosphorous, potash and many other nutrients required for plant growth.

It was pointed out to me recently that our ‘slurry problem’ is not a storage issue. Rather it is a ‘treatment’ challenge.

We have known for years that simply spreading slurry onto land using a tanker and splash plate is the most ineffective way of utilising this uniquely valuable resource.

And, to a large degree, dribble bars and injection systems do not move the debate forward to any great extent.

Allowing large quantities of nitrogen fertiliser to escape into the atmosphere in the form of ammonia is just totally wrong from every point of view.

It is a loss from a crop production perspective – an issue that is added to by the very negative environmental impact created by ammonia as a potent greenhouse gas.

Global stocks running low

Meanwhile, we are fast getting to a stage when animal manures will be the most valuable source of phosphorous available to farmers. This is because global stocks of mineral phosphate are running low. And the same may well be true, where potash is concerned.

We need some ‘blue sky’ thinking brought to bear on how best to ‘mine’ the nutrients in slurry and other animal manures.

Recycling these ultra-valuable crop, and animal nutrients, must be made a priority for agriculture. And this has to happen pretty quickly; otherwise, the challenge of feeding the nine billion people projected to inhabit this planet by 2050 will not be met.

Dry slurry?

It struck me recently that slurry and milk have one thing in common: they are predominantly made up of water. Yet, for the most part, it is feasible to dry milk down to its powder form without denaturing any of the nutrients contained within it. So why can’t we take the same approach with slurry?

Let me leave you with this thought. There are plans to invest heavily in anaerobic digestion plants throughout the Republic of Ireland during the period ahead. And there are already 200 such facilities now up-and-running in the North.

That I am aware of, the vast majority of these have no planned use for the heat produced as part of the electricity generation process. This truly is a waste, in every sense of the term.

Given this scenario, surely it would be feasible to include some of these plants in a trial in order to gauge the effectiveness of bolting-on a heat-driven slurry dryer; and to assess the fertiliser value of the resulting product.

The initial source of slurry would be the digestate emanating from the plants concerned.

How’s that for some ‘blue sky’ thinking on a very cold January day?

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