Products manufactured using hemp have the potential to play a significant role in improving the carbon and environmental performance of homes throughout Australia, a conference has heard.

(above image: Mulloway house by Otetto)

At the recent Hemp Connect forum hosted in Melbourne, Dr Ernesto Valenzuela, a senior lecturer in agricultural economics at La Trobe University, and Professor David Flemming, a professor of agricultural and resource economics also at Latrobe University, outlined findings from two recent reports that were published by the university (see here and here).

The reports explored the potential for a type of structural building product known as hempcrete to improve the environmental performance of new housing throughout Australia.

They concluded that hempcrete holds potential for greater use across Australia’s housing market.

Derived from cannabis, used in structural panels

Essentially speaking, hemp as used in industrial processes is a variety of the Cannabis sativa plant which is cultivated for fibre and seeds.

It is distinct from marijuana – which is also derived from cannabis plants – on account of its low tetrahydrocannabinol (THC) content.

In construction, hemp fibres can be used in fibreboard, insulation, and plaster.

However, a key use of the material involves structural insulated panels which are manufactured using a product known as hempcrete.

Hempcrete is a typically a mixture of hemp fibres, lime and water.

Structural panels which use this are typically manufactured by laying wooden frames flat and filling them with a hempcrete mixture.

Whilst hempcrete can be used in traditional construction, the reports focus primarily on its potential to be applied in a prefabricated, modular construction setting.

Important benefits

A critical advantage of hempcrete lies in the material’s environmental performance.

Because hemp captures carbon during its growth cycle and locks this into the final product, hempcrete can sequester carbon and store this away over the course of the product lifespan.

This means that the material is storing carbon that would otherwise be in the atmosphere and contributing to global warming.

A 2013 study found that hemp can sequester up to 165kg of carbon dioxide per cubic meter.

Thanks to good insulating properties, meanwhile, the material may also help to deliver lower energy consumption and reduced carbon emissions in heating and cooling.

Beyond carbon performance, hemp is both renewable and requires minimal use of pesticides, synthetic fertilizers and water relative to other fibre crops.

Hemp plants also help to improve soil health and support biodiversity.

In addition to its environmental benefits, Valenzula also says that hempcrete is fire resistant, durable and reusable, beneficial for indoor air quality (by managing humidity and reducing mould growth) and offers a high level of acoustic insulation or sound proofing.

Big potential

According to Valenzuela and Flemming, the potential for use of hempcrete in Australia’s homes and buildings is significant.

Primarily, this will be driven by a need to reduce carbon emissions as Australia targets 43 percent reductions in carbon dioxide by 2030 and net zero by 2050.

According to the Department of Climate Change, Energy, the Environment and Water, Australia’s building sector (not including civil construction) accounts for 19 percent of the nation’s energy use and 18 percent of direct carbon emissions.

With this in mind, the industry is being asked to do more.

As part of the 2022 update of the National Construction Code, the minimum performance requirement for new homes in terms of energy efficiency was increased from 6 star ratings under the Nationwide House Energy Rating Scheme (NatHERS) to 7 stars.

It is also possible that the 2028 update of the Code may include minimum requirements for ‘embodied carbon’ for the first time.

This relates to the carbon emissions which are associated with the materials and construction processes that into the building’s actual construction. It includes emissions which are associated with material extraction, manufacture and transport as well as those which are associated with on-site construction.

(image source: as above)

Challenges remain

Despite its benefits, market penetration of hemp and hempcrete across the housing space remains extremely low.

As things stand, there is no known reliable dataset which quantifies the material’s penetration into the building space. However, the annual number of homes which are constructed using hempcrete throughout Australia is thought to be in the hundreds only. This represents only a tiny proportion of the approximately 200,000 homes which are built around the nation each year.

Whilst many are optimistic about the opportunities which are available, some growers at the forum expressed frustration about the industry’s slow rate of growth.

In order for uptake to improve, report authors suggest that challenges need to be overcome in several areas.

First, there is cost.

In order to be competitive with other structural housing types such as weatherboard, brick veneer and full brick, report authors suggest that hempcrete panels need to deliver a consistent price of between $2,000 and $2,500 per square meter for a three-bedroom home (depending on the level of finish involved) and between $2,700 and $3,500 per sqm for a four-bedroom home.

For a range of reasons, there are challenges in producing substantial volumes at this price point whilst still delivering a viable return for farmers, decorticators (those who strip the bark off the plant) and manufacturers.

These include high costs of hurd (see below) production, high transport costs, low levels of production scale and low levels of vertical industry coordination.

Another challenge is a lack of standardisation of processes for production, design or certification when it comes to hemp products.

This can create lengthy approval processes as well as reluctance on the part of architects, builders and building surveyors to specify, use and approve designs which use hempcrete.

Other challenges include:

• Limited access to locally produced hurd (the woody inner core to the hemp plant’s stalk which is the part of the hemp plant that is used for construction).
• Builder resistance to change and tendency to work with products with which they are familiar.
• Current production processes which remain small, laborious and time-consuming.
• High costs of transport for hurd (due to the weight of the material) and risks in transportation of panels.
• A lack of availability of hydraulic lime (which is the best option to use in hempcrete) in Australia, meaning that the industry is reliant upon imported product.
• Low market awareness and a lack of information and understanding within the market of the benefits of hempcrete.
• The absence of a comprehensive life cycle analysis for hempcrete panels in Australia – a phenomenon which limits the appreciation of the environmental value of the product within the marketplace.
• A lack of consistent and meaningful government support.
• A lack of industry coordination – especially across the vertical supply chain.

(Hemp is costly to transport. Image shared by Ernesto Valenzuela during Hemp Connect.)

Actions recommended

In response, the report suggests a range of actions.

These are recommended to occur over the next five to seven years.

In relation to cost competitiveness, for example, the report recommends that the industry seeks to attract investment in large-scale commercial production facilities, improve industry coordination, improve training opportunities for tradespeople in working with hemp, work with governments to develop incentive programs and strategically identify optimal production sites which reduce transport costs.

To shift market focus away from pure cost, meanwhile, further recommendations include greater emphasis on life-cycle benefits and lifecycle cost savings as well as consumer awareness campaigns which highlight the benefits of hemp.

To address the lack of standardisation, meanwhile, the Australian Hemp Council is working with Standards Australia, the Australian Building Codes Board and other stakeholders to develop a series of Australian standards for hempcrete construction.

Once the standard is developed, there may be opportunities for the industry to put a case to the ABCB to have the new standard referenced in the National Construction Code.

Whole hemp product must be used

In relation to cost competitiveness, Hunter-based grower Bob Doyle goes further and says that the entire hemp product needs to be used.

In addition to the inner woody ‘hurd’ core which is used for housing, this includes the seed (which can be used for food, flour, oils and extracts) and the outer bast (which contains the long fibres used for textiles, rope or packaging).

For this to happen, Doyle says that greater communication is needed between the manufacturers, decorticators and growers.

First, he says that the industry needs to carefully consider which manufactured products can be made economically at a suitable profit for all concerned.

From there, manufacturers need to clearly define specifications which must then be used by the decorticator to produce the product for the manufacturer.

Decorticators, in turn, need to clearly outline their precise requirements to growers. This includes matters such as the length of chop required during harvesting, whether round bales are needed or square ones will suffice, requirements for retting (separating plant fibres by letting them lay on the ground to break down in weather) dry matter percentage, the amount of leaf which is allowed in the harvested crop and other requirements.

This, Doyle says, is critical. Only by selling the whole plant will the industry be able to move beyond niche market status and deliver a product which is cost competitive for housing.

Optimism remains

Despite frustrations about slow rate of uptake, Doyle remains upbeat about the potential of hemp.

“The opportunities that are in this industry are huge,” Doyle said.

“There really is a great opportunity in this industry.”

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