Self Grown Hemp for Construction

Wouldn’t it be ideal if you could grown your own hemp and then use it to build your home? 1 or 2 hectares of hemp stalk is potentially all you need to harvest enough building materials to build a house. Imagine that – growing your own house!  … but it isn’t a simple thing to do.

The hemp plant has four elements: seeds, leaves, fibers and a wooden core. The part you need for construction is the wooden core – also called the hurd or shiv. Separating it from the other elements of the plant requires effort. You need to grow the hemp, deffoliate it (remove the leaves) before harvesting, harvest or remove the seeds, harvest the stalk, let it ret (start decomposing so that the fibers can be separated from the hurd) and then decorticate it.

This finally step of decortication seems like the greatest obstacle – this is the process of separating the fiber and the wooden core. It can be done either through massive manual labor (of which I don’t yet have all the details – but it involves collecting the harvested stalks into small bales and then beating them to separate the fibers and wooden core) or in an industrial process. The indutrial process is usually designed to extract the fibers, the actual wooden shiv is simply a left over of that process.

It would be so much easier to grow your own construction hemp if decortication could be avoided – and this may be possible but my understanding is that it depends on the climate you live in. This research paper on Hemp-Concretes claims that it is possible to create hempcrete using both shives and fibers – BUT it is important to note that the research focuses on the structural aspects of the resulting hempcrete. It does not address the effect of fibers on insulation and breathability of the hempcrete.

Introduction of fiber to the hempcrete mix can cause humidity problems. When fibers are clumped together they tend to draw moisture and that is not something you want to happen in your wall. According to Steve Allin it is possible to add 5%-15% of fiber to the mix but not much more. This may be less of an issue in a hot and dry climate – but otherwise the risk seems unwarranted.

Maybe when the hemp industry matures it will be possible to cultivate stalks with very little fiber and a massive wooden core – which could then be used in whole? For now though it seems that self-grown hemp is not a feasibly reliable option for construction unless you have the means to decorticate it.

Information on Harvesting Hemp – Part 1

Inspiration

I am currently living with an inspiring notion that we will (1) be able to grow the hemp needed to build our future home and (2) that we will have enough land to grow a houses-worth of hemp every year so that someone else will be able to do the same.

Introduction

Though I have to say that the more I explore the world of Hemp the more doubts about this being a feasible goal. At the end of this post you will find some links and PDF’s I read and that led to my current understanding.

Hemp seems to be a relatively easy crop to grow. It’s strong, it doesn’t require pesticides, it grows pretty fast (~4 months) and it even renews the land in which it is grown. The more substantial challenge is harvesting and processing it.

Three Parts of Hemp

There are three parts to the hemp plant – each with it’s own uses:

  1. The seeds can be used for all kinds of food products, oils and other medicinal by-products.
  2. The fibers have all kinds of industrial uses (from clothes to cars) – they are the middle layers of the stalk covered by a thin protective layer.
  3. The hurd – the wooden core that is left over after the fibers have been extracted – which is the part popularly used (together with lime) for construction (although I have come across information that indicates that it is possible to use the fibers and curd together for construction – which means that they don’t need to be separated).

Some Hemp Harvesting Facts

  1. Seeds and stalk don’t mature together – they are (or at least should be) harvested at different times. Both the seeds and the fibers have (different) optimal times for harvesting – beyond which both lose some of the potency and qualities.
  2. The seeds don’t mature all at once – they tend to mature in two cycles. Harvesting time is when you think you can harvest the most mature crop (when some of the seeds may have decayed or lost their potency and others still not quite matured).
  3. Hemp is a tough plant – so you need resilient and strong harvesting tools. The strength of the fiber means it’s hard to cut down and the length of the stalk means it will catch on to and jam any moving part it finds (for example – combine machinery) – which means that you either need powerful harvesting machines – or that harvesting may be slow and tedious.
  4. Hemp is a tall plant (much taller then wheat or barley) – which means you need harvesting equipment that can reach up high.
  5. When the stalk is cut, it is useful to do it in such a way that it is then easy to collect into bales – if I understood correctly what this means is that the harvester needs to leave the cut stalks uniformly oriented on the ground.
  6. The stalks should be cut as long as possible – long fibers are generally better and more useful then shorter ones.
  7. It is possible to harvest both seed and stalk. Seeds go first (duh!) – but then you not only need tall harvesting equipment but it also needs to be sharp and fast spinning – so that the stalk is cut cleanly – leaving long fibers in tact.
  8. The primary processing for seeds is removing them from their shells – I still don’t have information on how that is done.
  9. The primary processing for stalk is separating the fibers from the wooden sheathe (this is called “decortication”- whichI am guessing comes from the idea of removing the core and, apparently, originates from a medical surgical process of separation). There are numerous methods for this – but generally they seem to be divided in two: industrial processes and organic/natural processes. I am less interested in the industrial aspect so I focused a bit more on the natural processes. Apparently the idea is to use water to cause decomposition of a kind of “glue” that keeps the fiber and curd attached. Usually natural dampness like dew will do the trick. You need to keep an eye out on the crop until separation begins – then you need to let it dry for a few days. I am not yet clear on all the details of this process.

All these facts seem to eminate from an industrial/financial view point. They are focused on creating optimal yields and financial returns. If harvesting and processing hemp can only be done using heavy and expensive machinery – that means that growing just a few acres or a hectare of hemp isn’t feasible.  I was somewhat discouraged by this. But …

Since hemp has been grown for hundreds of years (if not thousands) I am sure there is much knowledge on how to do it on a smaller scale – for home needs but I haven’t been able to find any information on this yet. It may require more manual labour but I am confident it is possible. Our needs are humble – maybe to build another small structure for meditation, enough seeds for eating, making oils … the needs of a small family.

I’ll continue to look for more home-oriented information on this – I promise to share it here when I do find it.

Resources and Further Reading

Links:

PDF’s: