It is encouraging to see the trend to conserve energy and reduce man’s impact on the environment increasing daily. In global terms, developed countries use energy and resources to fuel their construction industry that is wasteful and way beyond the ability of the planet to support such profligate consumption. Mass materials like cement and concrete cause significant pollution; use a lot of energy and non-renewable resources. Many of the materials such as insulation and finishes contain toxic chemicals like brominated fire retardants which can seriously damage our health as well as the ecosystem. (Environmental Building news 2004)
It has long been recognised that buildings and their use contribute significantly to CO2 emissions however it seems there are two main approaches to creating a lower impact on the environment.
There are those focussed on getting mainstream construction to be more energy efficient, even though they still rely on high embodied energy products such as cement, bricks, concrete and steel. This focus is based on retaining the same style of construction using the same materials with more insulation (petrochemical-based) and solar technology to “reduce” the impact. It would seem the intent is to appease the environmental conscience without pain. In the UK, the construction and use of buildings accounts for over 50% of the carbon dioxide produced. Studies have shown that up to 200kg of CO2 is emitted in the production of each square metre of walling for houses alone – equating to 40 tonnes for the walls of a typical house using double brick walls.
The other approach has been to look at low impact alternatives that also are healthier and less polluting in both their manufacture and construction technique. Helping to reverse the damaging effects of greenhouse gases, Hempcrete locks up around 110kg of CO2 per m3 of wall and provides one of the best value materials for low impact, sustainable and commercially viable construction.
Hempcrete or HLC (Hemp Lime Composite) is a composite construction material and building method that combines fast- growing, renewable anecofibre.com.aud carbon-sequestrating plant-based aggregates (hemp shiv) with a lime-based binder to form a lightweight material that is suited to solid walls, roof insulation and under-floor insulation and as part of timber-framed building. It also offers good thermal and acoustic performance and the ability to regulate internal relative humidity through hygroscopic material behaviour, contributing to healthier building spaces and providing effective thermal mass. It is formed by mixing together hemp shiv and a lime-based binder. The lime binds the hemp aggregates together, giving the material modest structural strength and stiffness. Lime also protects the shiv from biological decay, mainly through its ability to wick water away from the hemp shiv and its high alkalinity, as well as providing essential fire resistance. (Woolley and Bevan 2007)
A particular benefit of hempcrete is its capacity to sequester CO2 into the building fabric. As government policy becomes increasingly concerned with reducing carbon emissions and finding more efficient ways of meeting carbon reduction targets, it seems possible that hempcrete can make a major contribution to this, offering a genuinely zero-neutral solution to sustainable construction.
Transport and Carbon footprint
21.600 km by sea equals 332 km by road
65 km by container ship equals 1 km by light commercial truck
Bordeaux - Sydney = 11.216 Nautical Miles = 20.772 km
So a trip from Bordeaux port to Sydney port by boat equals a trip from Sydney to Coffs Harbour of 320 km
Add transport from St Astier (our hempcrete binder plant location in France) to Bordeaux port by road is 112 Km
Total is 432 Km
From North of Brisbane (possible hempcrete binder plant location) to Coffs Harbour is about 430 km.
So any job within a radius of 430Km* of our possible plant in North brisbane is worth freighting to when it comes to carbon footprint.
Any job bejond that* will have less carbon footprint for it's transport when freighted by sea from France.
(thanks to David from Ecospecifier)
Hemp
Industrial hemp is a different strain of Cannabis Sativa containing very little of the psychoactive substance found in marijuana. You simply cannot get high on industrial hemp. See this blog for more explanation.
Hemp is a genetically diverse species, with varieties adapted to a wide range of latitudes and climatic zones. It is a summer annual, short-day flowering plant, with 2-3 crops per year in some areas of Australia. The fibre of the hemp plant comes from the stalk, which is comprised of bast (the outer bark fraction of the stem) and the hurd (which is the inner woody core). Hemp as a fibre crop grows over the peak of summer, typically a 100-120 day crop harvested in January and February. It is a low cost crop, with minimal infield operations post planting. A grower requires an appropriate state licence or permit to grow industrial hemp. (www.ecofibre.com.au)
Hemp is far more productive than typical agro-forestry projects, producing annual, versatile biomass alongside more rapid CO2 uptake. It can produce a vast range of sustainable raw materials with an overall low environmental impact, as well as improving soil structure, using low fertiliser and no other chemical inputs (i.e. reduced agrochemical residues).
Hemp can be grown on existing agricultural land (unlike most forestry projects), and can be included as part of a farm's crop rotation with positive effects on overall yields of follow on crops. This, along with super versatility in diverse soil conditions and climates, makes hemp cultivation a viable and genuine potential large scale contributor to GHG mitigation. (www.hempglobalsolutions.com/science2.php)
It is estimated that hemp cropping will sequester an average of 10 tonnes of carbon dioxide per hectare. (www.hempglobalsolutions.com/science2.php)
Lime
Lime manufacture involves high temperature kiln operations to break down the limestone. Kiln temperatures will range from 900-1000oC depending on the composition of the limestone. Portland Cement, the basis of most concrete, is also made from burning limestone but requires higher energy outputs with kilns needing to reach temperatures of 1450oC and higher.
Find further information on the difference of lime and cement renders or the mineralogy of binders and the Effects of Free Lime content and Cement addition in Lime Mortars here.
The lime binder cycle for hempcrete is shown in the flowchart below:
NB: CaCo3 (limestone) goes the full circle from being broken down to carbonation when hempcrete is formed. As the hempcrete hardens from carbonation, it will eventually petrify the hemp and form limestone.
Hempcrete
Hempcrete is environmentally sustainable:
a) Carbon Sequestration
It is a carbon-sequestering building material from the growth of hemp to the carbonation of lime in the walls for the life of the building.
The breakdown of the carbon sequestration is as follows:
- In 1 cubic metre mix of hempcrete, emitted CO2 is:
- 110kg of hemp hurd = - 202 kg (CO2 absorbed)
- 220 kg of lime binder = +94 kg (CO2 released)
- Total sequestration = -108 kg/m3 of wall built
b) Energy Conservation
It reduces energy consumption because of its excellent insulation and airtightness. There is little heating or cooling losses from the building which means constant energy output to keep the building cool or warm is not required. Because hempcrete has low effusivity and high thermal inertia, it does not take as long to heat a house but once heated, it will slowly release heat back in when the temperature drops ... so the heater doesn’t need to stay on all night.
c) Recyclable
Hempcrete is fully recyclable. Any waste on site can be re-used in the next mix. If the building is being demolished, the hempcrete can be easily broken down and used in a new build. As landfill, hempcrete, being a natural product, will break down over the course of time, add lime and organic matter to the soil.
Hempcrete has no equal for its environmental and energy saving credentials in building materials.