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Phytotechnology with Biomass Production
removing pore water. Many degradative reactions are oxygen-dependent,
although some are anaerobic.
One good example of phytoremediation using trees for removing fuel contaminants from a shallow aquifer was reported by Nichols et al. (2014). In their
study, ~579,000 L of diesel, jet fuel, and gasoline (all moderately volatile) were
present at the start of the project in an area of two hectares. Poplar, willow, and
pine trees were planted at the site in 2006 with most of the 3250 trees being
poplars. When poplar and willow trees died, they were replaced by cuttings
from the healthy trees at the site. Soil-gas sampling was used to follow the
progress of the remediation and determined a 95% loss of total PHCs (TPH),
and a 99% loss of mass of benzene (very volatile). As the trees grew, their
ability to pump water increased and this was beneficial. In this example, the
TPHs were all liquids at ambient conditions. Methyl-tert-butyl ether (MTBE),
a highly water-soluble fuel additive, was taken up by the trees and released
to the atmosphere. As the rate of release to the atmosphere was limited by the
rate of evapotranspiration of the water that the MTBE was dissolved in, the
concentration of MTBE in the atmosphere was very small (Narayanan et al.,
1999), and in addition, MTBE has a very short atmospheric half-life on the
order of 3 days (Squillace et al., 1997). There is no doubt that other constituents passed through the trees at lower levels proportional to their water vs
lipid solubility. Toxicity to plants would limit this uptake for levels of benzene,
toluene, ethylbenzene, and xylenes. Less polar lipids, found in crude oil and
environmentally aged petroleum fractions, are generally much less toxic.
Combining the use of vascular plants and microbes (bacteria and/or fungi)
is proving to be a promising approach for degrading a variety of organic contaminants including PHCs. Studies carried out recently have largely focused
on the potential of endophyte and rhizosphere plant growth promoting bacteria to increase the efficiency of phytodegradation (e.g., Becerra-Castro et al.,
2013; Chlebek & Hupert-Kocurek, 2019). These bacteria, possessing catabolic
genes, mineralize organic contaminants within the plant or rhizosphere,
reducing their phytotoxicity, while promoting the growth and development
of plant root and shoot biomass (e.g., Afzal et al., 2014; Arslan et al., 2017;
Glick, 2010; Santoyo et al., 2016).
Cannabis sativa is an annual dioecious herb capable of growing to heights
of 5 m and having long tap roots. This plant has been grown since ancient
times for use in a wide range of applications. Fibers from hemp are extensively used in products that include fabrics and textiles, ropes, yarn, carpeting, construction and insulation materials, etc. (Johnson, 2014). The short and
woody fibers in the hemp’s stalk interior are known as “hurds” and are used
in the manufacture of animal bedding, paper, and composites. Hemp seed is
used in various foods and beverages and oil from hemp seed is widely used
in industrial oils, cosmetics, and pharmaceuticals. In addition, cannabinoids,
a group of compounds found in Cannabis (with the most notable being the
phytocannabinoid tetrahydrocannabinol (THC)), are used medicinally, spiritually, and recreationally (e.g., Bilalis et al., 2019). The term “hemp” is used
Phytotechnology with Biomass Production
removing pore water. Many degradative reactions are oxygen-dependent,
although some are anaerobic.
One good example of phytoremediation using trees for removing fuel contaminants from a shallow aquifer was reported by Nichols et al. (2014). In their
study, ~579,000 L of diesel, jet fuel, and gasoline (all moderately volatile) were
present at the start of the project in an area of two hectares. Poplar, willow, and
pine trees were planted at the site in 2006 with most of the 3250 trees being
poplars. When poplar and willow trees died, they were replaced by cuttings
from the healthy trees at the site. Soil-gas sampling was used to follow the
progress of the remediation and determined a 95% loss of total PHCs (TPH),
and a 99% loss of mass of benzene (very volatile). As the trees grew, their
ability to pump water increased and this was beneficial. In this example, the
TPHs were all liquids at ambient conditions. Methyl-tert-butyl ether (MTBE),
a highly water-soluble fuel additive, was taken up by the trees and released
to the atmosphere. As the rate of release to the atmosphere was limited by the
rate of evapotranspiration of the water that the MTBE was dissolved in, the
concentration of MTBE in the atmosphere was very small (Narayanan et al.,
1999), and in addition, MTBE has a very short atmospheric half-life on the
order of 3 days (Squillace et al., 1997). There is no doubt that other constituents passed through the trees at lower levels proportional to their water vs
lipid solubility. Toxicity to plants would limit this uptake for levels of benzene,
toluene, ethylbenzene, and xylenes. Less polar lipids, found in crude oil and
environmentally aged petroleum fractions, are generally much less toxic.
Combining the use of vascular plants and microbes (bacteria and/or fungi)
is proving to be a promising approach for degrading a variety of organic contaminants including PHCs. Studies carried out recently have largely focused
on the potential of endophyte and rhizosphere plant growth promoting bacteria to increase the efficiency of phytodegradation (e.g., Becerra-Castro et al.,
2013; Chlebek & Hupert-Kocurek, 2019). These bacteria, possessing catabolic
genes, mineralize organic contaminants within the plant or rhizosphere,
reducing their phytotoxicity, while promoting the growth and development
of plant root and shoot biomass (e.g., Afzal et al., 2014; Arslan et al., 2017;
Glick, 2010; Santoyo et al., 2016).
Cannabis sativa is an annual dioecious herb capable of growing to heights
of 5 m and having long tap roots. This plant has been grown since ancient
times for use in a wide range of applications. Fibers from hemp are extensively used in products that include fabrics and textiles, ropes, yarn, carpeting, construction and insulation materials, etc. (Johnson, 2014). The short and
woody fibers in the hemp’s stalk interior are known as “hurds” and are used
in the manufacture of animal bedding, paper, and composites. Hemp seed is
used in various foods and beverages and oil from hemp seed is widely used
in industrial oils, cosmetics, and pharmaceuticals. In addition, cannabinoids,
a group of compounds found in Cannabis (with the most notable being the
phytocannabinoid tetrahydrocannabinol (THC)), are used medicinally, spiritually, and recreationally (e.g., Bilalis et al., 2019). The term “hemp” is used