curated by Antonio Massa from birrificio Valdarno superiore
In the previous article we mentioned two different types of by-products that are left over from the process of brewing homemade beer: spent grain, and the hops trub sediment (or ‘dregs’) from the filtration process.
But what exactly are spent grains and dregs, and how can they be transformed from waste products into food or substances with agricultural purposes?
Spent Grains are formed when all the wort has been extracted from the ground malt grains. The spent grains are the fibrous outer layer of ground barley malt, leftover after they have been brewed (in this phase, they reach a temperature of 78° C).
In addition to the fibrous matter, spent grains also contain starch residue, so really, spent grains are fibers of high quality malt grains and starch which has been converted into simple sugars by means of cooking.
Spent grain is therefore a perfect semifinished product which has many uses for making food and for agriculture.
Uses of spent grains
Spent grains and food – Spent grains add flavour and nutrients (especially fibre) when added to dough mixes for bread, breadsticks, and cookies.
Spent grains for animal feed –The calorie value provided by spent grains is comparable to that of soy or corn, plants which require large quantities of water for cultivation. It would be wonderful to incentivate the collaboration between beer producers and animal-feed producers, or between artisanal breweries and local livestock farms.
Spent grains as charcoal –Through a preventive drying process it is possible to obtain biochar and using other methods vegetable pellets can be obtained.
Spent grains for compost – Spent grains can be composted, as they are cereal fibres. They can be buried underground or ensiled to produce fertile soil.
Hops trub is the leftover hops residue after the hops have been separated from the green beer wort.
The so-called hop cake is nothing more than the compacted hops flower residue, after the ‘whirlpool’, that is wet with beer wort.
If the brewer has used hops pellets to make his beer, the appearance of the trub will be similar to that of pesto.
The characteristics of trub make it an excellent candidate for use as a field conditioner for plant nurseries or fruit and vegetable patches.
Laboratory analysis has revealed the presence of nitrogen, potassium and phosphorus in trub, all elements which improve soil quality. Trub soil conditioner yields excellent results, especially in the
cultivation of flowers and roses.
Many studies have been carried out at the Valdarno Superiore Brewery, with research conducted by the Faculty of Agriculture of the University of Florence: four graduate theses discussing beer in relation to circular economies and sustainability have been written.