Hemp is considerably more efficient (high annual yields with low
agrochemical/fertilizer input) than the traditional annual bioenergy
crops (sugar beet and oilseed rape) and possesses similar greenhouse gas
mitigation potential to the perennial bioenergy crops Miscanthus and
willow (Finnan and
Styles, 2013). Annual bioenergy crops like hemp can be appealing
options for farmers to diversify and explore the bioenergy market
without the demands of perennials, namely high establishment costs and
long-term commitment (15–20 years) of their land to bioenergy
(Finnan and Burke,
2013; Finnan and Styles, 2013).
Hemp biomass has good combustion properties and could be used to
generate either heat or electricity
(Finnan and Styles,
2013). There are multiple biofuel options: Biogas, solid fuel
briquettes, bales, and bioethanol
(Kraszkiewicz et al.,
2019; Prade et al., 2012, 2011).
As hemp is an annual crop it can be readily integrated into crop
rotation cycles, thus not competing with food supplies and can therefore
contribute towards sustainable cropping systems
(Finnan and Styles,
2013). Moreover, hemp has been reported to improve yields of crops
subsequently grown thus complementing food production. Winter wheat
planted after hemp had 10–20% yield increases
(Bócsa and Karus,
1998), with similar observations recorded for soybean and alfalfa
(Adesina et al.,
2020). A low input crop, hemp can produce high yields similar to
switchgrass and sorghum but with lower nutrient and pesticide
requirements (Das et
al., 2017). Hemp offers the combined potential of an effective break
crop and an efficient energy crop, thus generating income while
promoting productivity. Break crops like hemp can be used to disrupt
pest cycles and the ability of hemp to tolerate high planting densities
suppresses weed growth, thus pesticide and herbicide requirements of
subsequently, cultivated crops are reduced
(Bhattarai and
Midmore, 2014). The hemp root system promotes soil health, as the large
taproots penetrate deep into the soil facilitating aeration, but
simultaneously forms soil aggregates to prevent soil erosion
(Amaducci et al.,
2008). Model analysis comparing the relationship between leaf nitrogen
status and photosynthesis rate in hemp, cotton and kenaf revealed hemp
to have a high photosynthetic capacity, even at low nitrogen levels
(Tang et al., 2017).
This provides an additional line of evidence that hemp may fulfil a
future niche as a sustainable bioenergy crop that can be cultivated over
a wide range of climatic and agronomic conditions.
11. Future prospects: Phytocannabinoids without Cannabis: In
vitro synthesis using cell cultures
Phytocannabinoids have high potential for medical but also recreational
use and therefore their production and extraction are of high commercial
interest. However, plant breeding and cultivation come with their own
challenges and phytocannabinoid yield and profiles can highly depend on
environmental factors. Cell cultures methods are a powerful tool for the
production of high-quality plant material in a manner that is time
efficient, seasonally independent, and which can satisfy good
manufacturing practice guidelines (Tekoah et al., 2015). This technology
has attracted a lot of attention as it can allow the harvesting of high
value products produced within cells in suspension or secreted into
their surrounding medium
(Weathers et al.,
2010). Improvement of culture growth kinetics and product yield can be
achieved via medium optimisation (Holland et al. , 2010; Ullischet al. , 2012; Vasilev et al. , 2013) and by selecting for
high-producing cell populations using techniques such as fluorescent
marker-based cell sorting (Kirchhoff et al. , 2012). Cell lines
optimised in these ways can subsequently be cryopreserved to ensure
consistent production going forward (Ogawa et al. , 2012).
Secondary metabolites, including pharmacologically valuable compounds
such as paclitaxel and scopolamine or transgenic proteins to be used as
vaccines, antibodies, immunomodulators and other therapeutics are
already produced in cell suspension cultures on a commercial scale
(Mountford, 2010; Paul
et al., 2015). Hence, this might be a promising avenue to produce
cannabinoids as well (Figure 10).