Whilst studying soil science as part of my National Trust Careership scheme, I read about how spent hops, a by-product from the brewing industry, can be an excellent source of organic matter in the garden. They can be used as a mulch on the soil surface where they will suppress weeds and help to retain moisture in the soil. They can also be dug into the soil where they will help to improve soil structure and water holding capacity as well as provide ‘food’ for soil organisms such as earthworms and beneficial bacteria. Spent hops also contain a decent amount of Nitrogen (1%), Phosphorus (1.5%) and Potassium (1%) and a full range of trace nutrients.
At Chartwell however, we are currently adding our spent hops that we collect from nearby Westerham Brewery to our compost heaps along with green waste such as grass clippings and shredded woody material such as pruned tree branches. Some of the hops that go in to the beers made by Westerham Brewery originally comes from another National Trust property, Scotney Castle. More information on the brewery and their tasty beers can be found at http://www.westerhambrewery.co.uk/
We have found that our composting system has been working much better this year, with the mix reaching a higher temperature and therefore producing a usable, well structured compost much quicker. If the composting material is kept well turned and moist then the process is even more successful. The dry hop casings improve the structure of the compost whilst the wet sand-like hop waste raises the moisture levels and improves the nutrient content. And to cap it off, the composting area at Chartwell now smells deliciously like a pint of local ale!