Agriculture Reference
In-Depth Information
potentially favourable impact vis-à-vis the
greenhouse effect. During its life cycle, one
m
2
of wall made from hemp cement, in 100
years, stocks between 14 and 35 kg of CO
2
eq per m
2
wall, depending on whether an
economic allocation or an allocation by mass
is used (Table 21.7). The storage of carbon
is due largely to the hemp straw, but is also
due to the wood and the lime contained
within the cement (due to the recarbonation
phenomenon).
As for the other largely negative impacts,
and in particular the consumption of fossil fuels
(between 370 and 394 MJ per m
2
), these need
to be compared against the results obtained for
other construction materials.
The production of the binder, followed by
the transportation stage, are the points that
account for the majority of the usage of non-
renewable energy, to the greenhouse effect
and photochemical ozone formation.
significantly only with regard to the waste
material produced.
Where walls of hemp cement are con-
cerned, hemp contributes to the unfavourable
impacts in a very marginal way (through the
waste material produced, use of non-renewable
energy, production of greenhouse gases and
destruction of the ozone layer), minimally (using
up/exhaustion of resources) and significantly
only with regard to air and water pollution.
The results of this study demonstrate that,
with regard to the greenhouse effect, both
thermoplastic compounds containing hemp
fibres and walls made of hemp cement on a
wooden frame perform well. This can be attrib-
uted to the carbon produced as a result of pho-
tosynthesis and stored in the raw material, that
is to say, the hemp. Furthermore, hemp
cement walls are long-lived and represent a
carbon store with a life expectancy of 100
years, with more carbon stored during the
course of the life cycle than is emitted. As for
thermoplastics, the substitution of a proportion
of the polypropylene with plant fibres reduces
the negative effect of thermoplastic compounds
on the greenhouse effect.
The results reported are due largely to the
raw product, hemp, whose production requires
little fossil fuel input and fits well into agricul-
tural production systems.
Furthermore, other environmental charac-
teristics can also be said to be favourable. Thus,
thermoplastic compounds containing hemp
fibre are less dense than existing thermoplastic
21.3.4 Conclusion and
future perspectives
Where thermoplastic compounds containing
hemp fibres are concerned, hemp contributes
to the potential negative impacts in a very
marginal way (through the using up of
resources, acidification, production of green-
house gases and destruction of the ozone
layer), minimally (air and water pollution) and
Table 21.7.
Potential environmental impacts, over 100 years, of a 1 m
2
wall of hemp cement on a
wooden frame and of a 1 m
2
wall of cement breeze blocks covered with an insulating PSE-plaster
material.
Wall made of hemp cement
on a wooden frame
Wall made of breeze
blocks and plaster
Environmental impacts
Exhaustion of resources (Sb eq)
1.3.10 ¯1
1.8. 10 ¯1
Atmospheric acidification (kg SO
2
eq)
1.0. 10 ¯1
1.1. 10 ¯1
Greenhouse effect (kg CO
2
eq)
−35.5
−28.8
Of which carbon storage (in kg CO
2
eq)
−75.7
0
Ozone layer (kg CFC-11 eq)
0.000227
0.000194
Photochemical ozone (kg C
2
H
4
eq)
5.4 10
-3
4.0 10
-3
Non-renewable energy (MJ)
394.2
432
Air pollution (m
3
)
1,024
4,290
Water pollution (m
3
)
6.7
8.9
