Not only is the JBF building product sustainable, but the production system itself will capture and reuse waste heat and water from flue gases. Water from the drying process is recycled into the blocks. As well up to 10% of the structural frame can be recycled. The resultant “carbon less-than-zero” building construction materials will reduce energy requirements in buildings and lower occupant operating costs. The result is a very affordable building construction system that sequesters more GHG than is emitted in its production and has very low embodied energy. The buildings constructed using the Just BioFiber block will use less energy to heat and cool and will contribute to healthier indoor air quality for the occupants. Each block directly sequesters 6.5 Kg of CO2 averaging 10 tonnes per home.
The following describes the GHG reduction by 4 components: embodied carbon as a function of the hemp and lime components; the energy efficiency of the buildings as compared to code built structures; the carbon sequestration directly in production; and, the continued sequestration in the block over its economic life. Total GHG reduction from 4 million JBF blocks produced annually is estimated at 88,400 t CO2e. Should Alberta growers achieve the hemp cultivation yields of the UK, that number could be as high as 104,200 t CO2e.
- Energy efficiency
The Just BioFiber blocks can be used for both residential and non-residential buildings, replacing both traditional wood frame and concrete block construction.
Building operating loads as a result of the effective R value (combined effect of the R value, no thermal bridging and thermal mass) of the JBF wall (R-33-35) compared to code built (R-20) 8,000 tonnes CO2e. Using RETScreen (NRCan Software for analysis of renewable energy efficiency and GHG) and Hot2000 (Produces EnerGuide rating used for energy efficiency ratings for residential homes) to compare a code build home (EnerGuide of 70) compared to a High performance home (EnerGuide of 88) with a comparative GHG emission of 6.4 t CO2e reduced to 2.3 t CO2e (due to mainly better R value) – 64% reduction in GHG. By extrapolating that result to GHG/sf we have an efficiency saving of 8,000 tonnes from 4 million blocks.
Energy efficiency from the plant operations has not yet fully explored, but there will be modest savings from the water recycle and likely waste heat capture in the equipment
- Carbon sequestration of the hemp plant in the soil and the plant
One hectare of industrial hemp plant absorbs 4 times the CO2 compared to trees. The JBF formulation requires 15,380 tonnes of hurd. As hurd represents about 33% of the hemp stalk, approximately 49,000 tonnes of hemp straw are required to produce 4 million blocks from 7,000 hectares of cultivated hemp. (Yield per hectare ranges from 5.5 to 8 tonnes per hectare so an average of 7 was assumed. This yield has been confirmed by AITF)
In terms of GHG sequestration, the UK report indicates 10 t CO2e is absorbed per hectare for a total of 70,000 tonnes of CO2e.
The UK report was derived as follows:
- Every tonne of industrial hemp stems contains 0.445 tonnes carbon absorbed from the atmosphere (44.46% of stem dry weight).
- Converting carbon to CO2 (12t of C equals 44t of CO2 (IPCC)), that represents 1.63 tonnes of CO2 absorption per tonne of UK Hemp stem harvested. On a land use basis, using Hemcore’s yield averages (5.5 to 8 t/ha), this represents 8.9 to 13.4 tonnes of CO2 absorption per hectare of UK hemp cultivation.
- For the purposes estimation, we use an average figure of 10t/ha of CO2 absorption, a figure we hold to be a reasonably conservative estimate. This is used to predict carbon yields, but CO2 offsets will be based on dry weight yields as measured at the weighbridge.
- The roots and leaf mulch (not including the hard to measure fibrous root material) left in situ represented approximately 20% of the mass of the harvested material in HGS’ initial field trials. The resulting carbon content absorbed but remaining in the soil, will therefore be approximately 0.084 tonnes per tonne of harvested material. (42% w/w).
- Using Hemcore’s UK yield estimates (5.5 – 8 t/ha) this represents 0.46 to 0.67 tonnes of carbon per hectare (UK) absorbed but left in situ after hemp cultivation.
- That represents 1.67 to 2.46 t/ha of CO2 absorbed but left in situ per hectare of UK hemp cultivation.
- Final figures after allowing 16% moisture (Atmospheric ‘dry’ weight) are as follows:
- CO2 Absorbed per tonne of hemp stem 1.37t
- CO2 Absorbed per hectare (stem) (UK) 7.47 to 11.25t
- CO2 Absorbed per hectare (root and leaf) UK) 1.40 to 2.06t
On a more conservative basis analysis from Brandon Pitcher, Sustainability Leader in the US suggests a combined CO2 sequestration of 5.225 t of CO2e reflecting a potential Canadian yield per acre of 4.5 tonnes. Consequently, the hemp-only GHG adsorption would be about 54,000 tonnes at this lower yield.
- Carbon sequestration through processing
The curing of the blocks uses 6,500 tonnes of CO2e annually at full production of 4 million blocks). Pilot trials by Just BioFiber over the past year have indicated an absorption rate of 1.625 kg/block of CO2 is absorbed during the curing process for the block. The curing room monitors and records the humidity, temperature and CO2, levels for each batch.
- Carbon absorption of the blocks over the life of the building (100 years) = 19,500 t CO2e for each year of production of 4.5 million blocks. Of course the rate of adsorption will decline over time as the lime carbonates and returns to stone.
While lime-based adhesive, exterior stucco and interior plaster also contribute to the carbon adsorption, the emissions from processing are being recaptured so this aspect of the system are viewed to be carbon neutral.
In terms of baseline emissions benchmarking, the most relevant study supporting the GHG benefits from hemp-lime construction was produced in 2010 by Marabel Clark (MSc Architecture: Advanced Environment and Energy Studies, Machynlleth, Powys, Wales). This study comprehensively compared the embodied carbon and embodied energy in various forms of construction. She concluded that the net embodied carbon from hempcrete of -17.6 kg CO2/m2 compared favourably to medium density concrete blocks with comparable insulation of 33.3 kg CO2/m2. Extrapolated to 4.5 million Just BioFiber blocks (1.2 blocks/sf), that is a benefit of 15,770t CO2 including the embodied carbon of the lime.
Since 2007. in Alberta, the Specified Gas Emitters’ Regulation (SGER) enabled monetization of the GHG savings. Protocols have been established for offsets that can be purchased by large emitters facilitating this carbon trade. Beginning in 2016, Alberta has extended the carbon pricing system to all forms of GHG emissions and has increased the price from $15/tonne to $20 with a further price increase scheduled for 2017. For the purposes of the financial prospective for Just BioFiber, offsets values have been established where sequestration can be measured and is in direct control of JBF. These offsets amount to about 6.5 kg/block that has been used for our GHG Environmental Benefits.