Hemp & Lime Part 2
This episode discusses the bigger picture of hemp as a building material and the current barriers to using it more broadly. See the previous episode for construction details.
The hemp we used was grown and processed by La Chanviere, a farmer cooperative in France.
Despite the recent surge in hemp farms in the United States, there isn’t yet a source in the US that grows and processes hemp to be used reliably as building material. We wanted to use hemp in this project in part to make a case to change that.
As New York is gearing up to meet its climate goals, “growing” a natural building material industry can play a significant part. Hemp farming is considered regenerative. It improves the nutrient level in the soil and does not need pesticides or herbicides. Hemp farming is also in its infancy.
Hemp was outlawed in the United States in 1937¹— more than 70 years ago, enough to lose the generational knowledge of growing and harvesting, let alone the infrastructure. Prior to that, industrial hemp was grown on many farms in the United States especially in the South.
New York loosened regulations for growing hemp in 2016 and the 2018 Farm Bill removed hemp and hemp seeds from the Drug Enforcement Administration’s (DEA) schedule of Controlled Substances. Since then a growing number of farms — big and small — have applied for licenses to grow cannabis, primarily to extract oil and then process it into various Cannabidiol (CBD) products. For high CBD yield, unpollinated, bushy, widely spaced female plants with many flowers are desired. Grain and fiber hemp crops — used for hempcrete include both male and female plants and are planted much more densely, producing tall slender plants.
Hempcrete as a building material is essentially derived from the waste of these tall plants grown for its fiber. The fiber is “retted” off the stalk and the remaining core then goes through a decorticator — a machine that chops it into hurds.
In 2021 about 32,000 acres of hemp were farmed in New York State by growers of all scales from several hundred acres to small backyard farms)². For scale comparison, about the 55,000 acres of apple orchards are farmed in New York State³.
But the hemp industry has seen recent challenges. An oversupply of CBD together with strict regulations on how to sell it, depressed prices⁴. The hemp plant can be used in more than 200 ways, CBD oil is just one of them. Hempcrete is another. It requires specific infrastructure for processing and distributing that currently doesn’t exist in the U.S. It is also ultimately dependent on establishing a market as well as recognizing hemp and its properties by building codes, especially fire rating.
That’s a lot of missing pieces or “chicken and egg” scenarios to move forward in making this super-sequesterer of carbon more widely used and profitable beyond its association as an illegal substance. In 2020, more than 900,000 single-family homes were built in the US. This number is projected to be more than a million for 2022. Imagine the opportunity for hemp and the building industry to become one of the building blocks of a carbon neutral future. We would need to harvest xxxx acres of industrial hemp to supply 1 million homes. Imagine the amount of low carbon jobs this could generate in farming, in processing and in building — growing a pool of experts in working with hemp from a handful to thousands.
Farmers need support investing into infrastructure — specifically the decorticator, the machine used to chop up the core of the stalks into hurd. More research and experience is needed to cultivate plants with a high yield in fiber. More built examples that use hempcrete as insulation help to make the case for hemp as a healthy and low-carbon alternative to synthetic insulation that can be grown, processed and used locally — in turn creating low-carbon jobs from source to end-user… and building codes need to be updated to better integrate and understand the performance of biogenic materials.
We would like to use the two micro-homes at Wally Farms to continue the conversations that others have started. Below is a list of additional resources on this topic. At the top of this list –and a great introduction to the topic– is the Hemp + Lime Guide and Podcast produced by Parsons Healthy Materials Lab.
New York State Industrial Hemp Research Initiative
Alex Sparrow, William Stanwix (2014): The Hempcrete Book, Green Books, Cambridge, UK
Chris Magwood (2016): Essential Hempcrete Construction, New Society Publishers, Gabriola Island, Canada
The US Hemp Building Association supports and advocates for hemp building professionals, projects and materials in the United States and holds an annual event, the US Hemp Building Summit
Hempstone offers trainings and workshops and shares a lot of their own lessons learned on their blog
Lancaster Farming’s Podcast on Industrial Hemp covers all sorts of topics touched on in this and previous article.
The Endeavour Centre in Ontario, Canada offers workshops and resource on building with biogenic building materials
The Hemp Building Association keeps an inventory of structures built with hemp. This summer, our hempcrete builders also completed The Cape Cod Hemp House, which used hempcrete even in its roof.
Notes
¹ Parsons Healthy Materials Lab (2019): Hemp+Lime: Examining The Feasibility of building with Hemp and Lime, Report, 2019
³ https://www.applesfromny.com/food-service-retail/ny-apple-industry-facts/
⁴ https://www.pewtrusts.org/en/research-and-analysis/blogs/stateline/2021/07/09/the-hemp-boom-is-over-what-now
