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Phytotechnology with Biomass Production
(Construction Manager Magazine, 2017). Once framed, Miscanthus bales
are placed within the frame in a manner similar to that employing wheat
straw bales. The demonstration project was a collaboration between the
University of Aberystwyth, the Centre for Alternative Technology, UK, and
Terravesta (a company specializing in Miscanthus technology). In addition to taking advantage of Miscanthus as insulation, a primary goal is
to reduce the large carbon footprint associated with conventional housing
construction.
As an insulation material, harvested product may be used directly.
However, there are several processing alternatives in using Miscanthus for
insulation (Moll et al., 2020). A comprehensive review of insulation materials from biomass is available (Liu et al., 2017). Low thermal conductivity
is important in insulation materials. In some applications sound absorption
is very important as well. There is a growing interest in renewable materials because of the importance of reducing greenhouse gas emissions. This
has resulted in an increase in the use of natural biomass insulation materials
(Bozsaky, 2019) with a patent being issued for such applications (HuesemannLammert, 2006).
In 2012 Karl Schock, a German engineer, began the development of an
insulating board based on Miscanthus or Napier grass. These are now fabricated through a German company, ISOCALM (GmbH, 2012), and are marketed as plaster carrier mats with thermal insulation. The reported thermal
conductivity is 0.45 W m −1 K −1 .
Cardenas et al. (2015) demonstrated the use of Miscanthus as a block-type
insulation material. While exploring formulations and processing conditions, thermal conductivities ranging between 0.079 and 0.116 W m −1 K −1 were
obtained. The flexural strength of the Miscanthus product resembled that of
expanded polystyrene, type IX.
Biomass insulation materials can be used in the natural form as some of
the examples above illustrate. However, two obvious issues of concern with
thermal insulation applications are fire safety and the impact of biological
organisms using the Miscanthus as a food source. Any application as an
insulation material must meet product standards related to fire safety. The
integrity of the material must remain even if microbes and other organisms
are present. Additives such as borax and aluminum sulfate may be added to
improve fire resistance and reduce mold growth (Lopez Hurtado et al., 2016).
Formulations have been reported which include ~1.75 wt.% borax, 1.75 wt.%
sodium carbonate, and 0.5 wt.% fungicide.
The experience gained from formulating cellulose insulation with recycled paper may well be applicable. The thermal conductivity of cellulose
insulation is approximately 0.040 W m −1 K −1 ; that value increases with moisture content. Low moisture content is desirable as it does not support mold
growth. Borate salts, boric acid, and aluminum sulfate are often mixed into
cellulose fibers to prevent combustion and mold growth (Lopez Hurtado
et al., 2016).