One of the key issues with transitioning to stock-free agriculture in Scotland is that approximately 86% of the total land area is classified as Less Favoured Area (LFA), which means that growing human-edible crops is often severely disadvantaged if not completely impracticable (Scottish Government, 2019). While there are other alternatives like ecosystem restoration and farm enterprise diversification, it is quite understandable that many farmers and crofters are reluctant to give up food production entirely.
In this regard, one promising stock-free alternative is the production of leaf protein concentrate or ‘leafu’ (coined by the late Michael Cole, a pioneer of leafu in England). Leafu goes by many names (leaf concentrate, leaf curd, leaf protein, leaf extract) but in essence, it is a nutrient and protein rich food for human consumption. It is made by a process called leaf fractionation. This consists of first reducing lots of young leaf matter to a pulp, pressing the juice from this pulp, then heating the juice to above 90 degrees Celsius, which causes a green curd (i.e. the leafu) to form on top that is then skimmed off, strained and used fresh or dried. To get a better understanding of its production process, we recommend watching this video giving an overview of leafu, and this video which covers leafu production at the smallest scale. Interestingly, additional steps can be taken in the leaf fractionation process to create leaf protein isolate (watch here), a colourless and neutral tasting version of leafu.
There are several major benefits to going through the somewhat complex process of making leafu. Firstly, the leaf fractionation process enables us to make many inedible leaf crops fit for human consumption, and in the case of edible but unconventional leaf crops, they can become more palatable or easily consumed. This opens up a wide range of plants that easily grow in LFAs for human consumption, from assortments of wild weeds to nitrogen-fixing green manures, and even grasses. However, several factors such as plant toxicity, ease of harvesting, yield, taste of the final product, and the management of soil fertility will influence what species are most practical to grow.
From speaking with SRUC researcher Dr. David Lawson – who has been studying leafu production at two trial sites in Scotland – white clover has so far proved a great candidate for leafu production across the country. Producing leafu from white clover should be feasible anywhere in Scotland where silage or hay can be made. Whilst yields will vary depending on your soil and local climate, white clover can typically produce 800kg of dried leafu from 8 tonnes of clover (dry weight) per hectare per year. This is harvested from mid-May to the end of September, with an expected 4 harvests at intervals of 4-6 weeks. According to David, processed leafu can be stored in two ways: drying it at about 80 degrees Celsius or acidifying the fresh leafu paste which effectively transforms it into a ‘pickled’ state.
|Food||Protein content (%)||Grams of protein per hectare of land per year|
|Dried White Clover Leafu||48*||384,000*|
|Beef Steak||31a||6,112 (beef herd)b|
In terms of nutrition, leafu has several beneficial qualities regardless of which plant species are used to produce it:
“Leaf concentrate is an extremely nutritious human food. It is approximately 50% (dry weight) high-quality protein, containing all essential amino acids, together with numerous micronutrients, principally β-carotene and iron. Various anti-nutritional components are largely removed by the fractionation process.” (Davys et al., 2011, p.341).
Looking specifically at white clover leafu, David observed it to have a similar quality, containing 48% protein as well as good amounts of all essential amino acids. Another benefit of leafu is that only relatively small amounts of it are needed to have a significant nutritional benefit. For example, “…a daily serving of 10 g of dried leaf concentrate has proved effective in alleviating deficiencies in vitamin A and iron.” (p.341) and the absorption of iron in leafu can be easily improved by eating it alongside vitamin C rich foods (Davys et al., 2011).
With leaf fractionation, the final product, leafu (~5% weight when moist), only represents a small percentage of the original plant matter, so the two by-products: whey (~50% weight) and fibre (~45% weight) make up the remaining bulk. While both by-products are great fertilisers when returned to the land, the fibre is also a nutritious animal feed which could be sold to animal sanctuaries for example. The whey can also be added to the fibre for animal feed, and on its own can be used as a substrate for fermentation. David’s analysis of the whey and fibre showed that they both have significant amounts of N, P and K, with the fibre’s N-P-K ratios being very similar to farmyard manure. He also mentioned that the fibre has potential as a product for the textiles market.
Indeed, there are still many applications to be explored for leafu and its two by-products. For instance, David looks forward to seeing how other productive crop and weed species can be utilised, including using more parts of common crops like the leaves from potatoes. A lot of the current research efforts into leafu taking place in Denmark, Germany, Ireland and the Netherlands should certainly shed more light on leafu’s potential.
All in all, leafu production could play a key role in helping Scotland adapt to and mitigate climate change, as well as improving food security and public health. By producing leafu, the Highlands and Islands of Scotland could continue to be a valuable regional producer of protein (replacing animal protein with plant protein). Not only could this help alleviate pressure on prime agricultural land, freeing it up to grow other important crops like staple foods, but it could free up land to be used for rewilding and diversification. As David said to us, producing leafu is like running a dairy in some regards, and in this sense I think it strikes a good balance of resembling traditional uses of land while producing a food that is more sustainable and nutritious.
If you are a farmer or crofter interested in pioneering leafu production, Dr. David Lawson is looking for farms and crofts to work with on his research trials. In addition, Farmers For Stock-Free Farming are in the process of putting together a RISS group for leafu. Feel free to contact us and we can add you to the group once its established. If you want to learn more about leafu specifically, contact me at email@example.com and I can provide you with additional resources.
Reference: Davys, M.N.G., Richardier, F.C., Kennedy, D., de Mathan, O., Collin, S.M., Subtil, J., Bertin, E. and Davys, M.J., 2011. 18 Leaf Concentrate and Other Benefits of Leaf Fractionation. Combating Micronutrient Deficiencies: Food-based Approaches, p.338.