BRING OUT YOUR DEAD!

fibre), wood fibre, and composted bark. Estimates of current use highlight that over 50 per cent of the Irish horticultural sector is still reliant on peat; hence the cessation of supply is having a major impact.

A survey of growers was carried out by UCD horticulture student Zoe Valentine, at the Irish Hardy Nursery Stock Association trade show at Whites Agri Premises in Lusk, Co Dublin, on 21 February 2023.

According to the survey, wood fibre was the most popular alternative material to peat, with over 50 per cent usage in the sector among the growers surveyed. Four out of eight companies solely use wood fibre as an alternative material. All those surveyed agreed that one of the impacts of switching to peat alternatives is the high cost and limited availability of the substitute materials.

But peat is also rising in cost: one of the growers reported an almost doubling in production costs associated with peat compost in one year. The cost of peat for one participant surveyed grew from €140K in 2022 to €260K in 2023. Growers are being forced to switch to alternative materials as a matter of both economic and environmental urgency.

water regulation. Herbaceous plants in particular suffer in the drier conditions of bark-dominated composts, and are often seen wilting and drying, as bark and wood fibre composts struggle to retain any moisture and are extremely prone to drying out.

With the race on to find suitable compost alternatives, Teagasc’s Ashtown Food Research Centre in Dublin 15 have been carrying out some impressive largescale trials using various ratios of coir, wood fibre and peat.

WHAT ARE SUSTAINABLE ALTERNATIVES TO PEAT?

The Revolution Farm & Kitchen, a saucemaking and mushroom-growing business project based on campus at University College Dublin, uses various compost mixes that contain bark shavings and spent coffee grounds. They also grow their mushrooms in wheelie-bins.

Inspired by the projects at Teagasc Ashtown and Revolution Farm, Zoe carried out an experiment to build a novel compost using only locally-sourced materials which are widely available.

The first material Zoe selected was oak bark shavings, a renewable resource rich in carbon and organic matter. The oak shavings used for the experiment were re-purposed from the spent mushroom composts of Revolution Farm & Kitchen.

Oak is a fairly high-end timber material, but the oak bark shavings Zoe used are a byproduct of an industry that we’ll all have to avail of eventually – the funeral industry. Many coffin manufacturers in Ireland use oak.

The second material Zoe picked

As many in horticulture are aware, the cessation of large-scale peat harvesting is forcing the industry to explore alternative materials as growing media, such as coir (coconut

The Quest For Peat Compost Replacements

One clearly observed negative effect of growing in wood fibre and barkdominated composts is

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QQI Level 6 Advanced Certificate for her experiment was spent coffee grounds, a well-known viable addition to compost. Coffee contains high amounts of nitrogen and other beneficial compounds that can improve the nutrient profile and texture of compost. Ground coffee is a rich source of nitrogen, which is essential for plant growth. extremely high or low in a compost, the plants growing can suffer either from deficiency or toxicity, so getting the pH balance right of any new compost is key.

In addition to nitrogen, coffee also contains other beneficial compounds such as potassium, magnesium and calcium.

Mixing materials such as coffee and moss – which have high pH – with the lower pH material of oak shavings, resulted in lowering the pH. Coffee and oak shavings combined had a pH of 5.6, a move in the right direction. While the figure is nowhere near the lows of solely peat-based composts (4.5-5), it is comparable to current peat alternatives with their pH of 5.7. The coffee, moss and oak mix had a higher pH of 6.

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