«Abstract Recently, researchers have drawn their attention to industrial hemp ( Canabis sativa L.) and stinging nettle ( Urtica dioica L.), as ...»
Features of Carbon Stock in the Biomass
of Industrial Hemp and Stinging Nettle
B. Butkutė, I. Liaudanskienė, Z. Jankauskienė, E. Gruzdevienė,
J. Cesevičienė and K. Amalevičiūtė
Recently, researchers have drawn their attention to industrial hemp
( Canabis sativa L.) and stinging nettle ( Urtica dioica L.), as feedstocks, potentially
having a wide nonfood application. The aim of the present work was to compare dry
matter (DM) and carbon (C) yields as well as C concentration in the above-ground biomass, stems and shives of the mentioned crops. In this chapter, extra attention has been paid to the C accumulation in stems and shives, since stems are a more environmentally friendly resource for solid biofuel compared to the whole above- ground part of the plant, and shives are an agricultural waste.
Field experiments with industrial hemp (eight varieties) and stinging nettle (one wild nettle and two treatments of fibre nettle clone) were carried out during 2010–2012. Dew retting and water retting were used to extract the fibre. C concen- tration in the samples of hemp and nettle was determined by wet oxidation with dichromate.
DM yield of the above-ground biomass of hemp amounted to an average of 10607 kg ha− 1, of stems 9063 kg ha− 1 with high C concentrations of 555 and 568 g kg− 1 DM, respectively. DM yield of the nettle declined along with a harvest year and ranged from 11604 kg ha− 1 (2010) to 5596 kg ha− 1 (2012) averaging B. Butkutė () · I. Liaudanskienė · J. Cesevičienė · K. Amalevičiūtė Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, Instituto al. 1, Akademija, Kėdainiai district, LT-58344, Lithuania e-mail: email@example.com I. Liaudanskienė e-mail: firstname.lastname@example.org J. Cesevičienė e-mail: email@example.com K. Amalevičiūtė e-mail: firstname.lastname@example.org Z. Jankauskienė · E. Gruzdevienė Upytė Experimental Station, Lithuanian Research Centre for Agriculture and Forestry, Linininkų 3, Upytė, Panevėžys district, LT-38294, Lithuania e-mail: email@example.com E. Gruzdevienė e-mail: firstname.lastname@example.org © Springer International Publishing Switzerland 2015 17 A. Sayigh (ed.), Renewable Energy in the Service of Mankind Vol I, DOI 10.1007/978-3-319-17777-9_2 18 B. Butkutė et al.
7589 kg ha−1 per trial. DM yield of wild nettle was more than twice as low as that of fibre nettle clone (on average 3945 kg ha− 1 vs 9411 kg ha− 1).
C stock in stems of hemp and nettle amounted to an average of 5149 and 3719 kg ha− 1, respectively. DM yield was a weighted factor for C yield.
Shives, which are the woody residue left over from the processing of hemp and nettle straw appeared very rich in C the concentration of which in hemp shives varied in the range of 564–602 g kg− 1 DM and in nettle shives 543–596 g kg− 1 DM. The retting method (R) significantly ( P 0.01) affected the C concentration in nettle shives.
The high heating value (HHV) of biomass, stems and shives of hemp and nettle was determined, and the theoretical accumulation of CO2 in biomass per ha was calculated.
Results of this study showed that the hemp and fibre clones of stinging nettle could be promising candidates for bioenergy production. The CO2 content fixed into the biomass of the studied crops might contribute towards the reduction of climate warming.
Keywords Bioenergy plant · Shives · Carbon · Dry matter yield (DMY) · Canabis sativa L · Urtica dioica L
2.1 Introduction Today, it is clear that the development of Europe’s renewable energy resources is a crucial element in the battle against climate change . The fight against climate change and the depletion of fossil fuels has forced humanity to “decarbonising” the economy . Burning fossil fuels uses “old” biomass and converts it into “new” CO2, which contributes to the “greenhouse” effect and depletes a non-renewable resource . The need for CO2 management, in particular capture and storage, is currently an important technological, economical and global political issue and will continue to be so until alternative energy sources and energy carriers diminish the need for fossil fuels . A plant used for biomass energy grows by removing CO2 from the air through photosynthesis . Carbon (C) accumulated in biomass through CO2 fixation can be easily converted into usable energy . Biofuel from energy plants is considered at least as “C neutral”: CO2 that is released in burning is returned to the biomass from the atmosphere during photosynthesis and returned for a cycle of new growth [3, 5].
Currently, researchers are focusing attention on hemp ( Canabis sativa L.) and stinging nettle ( Urtica dioica L.), as high yielding multipurpose feedstocks. Growing well in Central Europe, both hemp and stinging nettle are promising candidates for nonfood market production: textile, paper, building industries as well as bioenergy [6–11]. Hemp is an annual monoecious or dioecious plant and it is considered as being a crop that requires no pesticides, since it outcompetes weeds, uses little fertiliser or irrigation in temperate areas and potentially causes little land use change 2 Features of Carbon Stock in the Biomass of Industrial Hemp and Stinging Nettle 19 since it can be grown on marginal land (though it will require more inputs if not grown on cropland) . Industrial hemp (variety Futura 75) grown in Northern Europe, yielded an average of 14.4 Mg DM ha− 1 and exhibited satisfactory net energy yields per hectare [9, 13]. The stinging nettle is a common dioecious herbaceous perennial plant that grows on ruderal sites, in gardens, at the edges of forests and in wooded areas of the riverine floodplains . Nettle is practically not grown commercially in Europe . The existing areas cover experimental plots. Several new nettle clones have been selected and characterised by high fibre content and strong tillering . The trials with the clones of fibre nettle have been conducted in Austria, Germany and Italy [8, 16, 17]. The annual dry matter yield (DMY) of nettle in boreal growing conditions ranged from 6–10 Mg ha− 1  and DMY of stalks of five clones fluctuated from 2.3–9.7 Mg ha− 1 . Clones of fibre nettle were successfully tested as bioenergy crop, mainly for the purpose of anaerobic digestion [18, 19].
Shives are the woody residue left over after the processing of stalks (hemp, nettle, flax or other fibrous crop) on target for fibre extraction. This agricultural waste could be used as a renewable source for composites, combustion or other forms of bioenergy [20,21].
Since C containing compounds from the biomass generate a principal amount of biomass energy, we devoted our attention to the features of C stock in the above-ground biomass of hemp and stinging nettle and its fractions—stems and shives.
2.2 Material and Methods
A field experiment was carried out in the Central Lowland of Lithuania (55°39′11″N 24°13′59″E) at the Upytė Research Station of the Lithuanian Research Centre for Agriculture and Forestry on an Eutri-Endohypogleyic Cambisol ( CMg-n-w-eu) . The study involving eight monoecious varieties of industrial hemp and three treatments of stinging nettle (one wild nettle and two treatments of fibre nettle clone) was carried out during 2010–2012 in three replications. The hemp variety (V) “USO 31” (of Ukrainian origin) is known as a very early variety. Polish varieties “Beniko” and “Bialobrzeskie” are considered as medium-early in the country of their origin. The other five hemp varieties are French in origin and differ in earliness: “Fedora 17” is early-maturing, “Felina 32” and “Santhica 27” are medium-late maturing, “Epsilon 68” is late-maturing and “Futura 75” is a very late-maturing variety. The seed rate of hemp was 50 kg ha− 1, interrow spacing was 10 cm. Hemp was sown at the beginning of May, and harvested when the first mature seeds appeared (in September or October, depending on the year and variety ripening). In all experimental years, the V “USO 31” was harvested 0.5–1 month earlier than the other varieties: on September 9 in 2010, September 13 in 2011 and September 19 in
2012. The rest of the hemp varieties were harvested on October 4, September 22–23 and October 15–16, respectively.
20 B. Butkutė et al.
The current study on stinging nettle was a follow-up of the experiment where nettle has been cultivated since 2008. The wild stinging nettle was planted at a density of 60 × 60 cm and clones of fibre nettle—at two densities: 60 × 60 and 60 × 100 cm. Stinging nettle was cut at the end of May—beginning of June for testing biomass of young plants as food ingredient. After regrowth, stinging nettle was harvested when seeds were mature in the lower part of the inflorescence: at the end of August in 2010, on September 12 and 4 in 2011 and 2012, leaving stubble of up to 15 cm height. The biomass harvested at this time was studied as a feedstock for industry (textile and bioenergy).
Since we investigated stinging nettle and hemp as multifunctional plants, the dew retting and water retting were used to extract fibre. Shives obtained after retting were evaluated as a feedstock for solid biofuel.
The growing seasons were abundant in precipitation, whose amount was distributed unevenly over the period, but generally the weather conditions were favourable for hemp and stinging nettle growing.
C concentration in the samples of hemp and nettle was determined by a spectrophotometric procedure after wet oxidation of plant material with dichromate [23, 24]. In this chapter, extra attention has been paid to the C accumulation in stems and shives, since stems are a more environmentally friendly resource for solid biofuel compared to the whole above-ground plant part, and shives are an agricultural waste. Samples of hemp ant nettle stems were analysed for C every year. C in shives was established in the samples of 2010 and 2011 harvest years and in the samples of above-ground mass of 2010 harvest year. C concentration in above-ground biomass of 2011, 2012 harvests was calculated from C concentration in stems using coefficients 0.9774 for hemp and 0.9664 for nettle. These coefficients were obtained from the data of 2010 harvest as a ratio of C in the respective samples of plant aboveground biomass and stems. Samples for the total nitrogen (N) concentration were analysed by the Kjeldahl method. The ash content was determined by the method consistent with LST EN 14775  with mass incineration at (550 ± 10) °C. Klason lignin was analysed using the procedure NREL LAP 003 . Gross calorific value (GCV) or high heating value (HHV) was measured using an IKA bomb calorimeter (C 200, Germany) following the LST EN 14918 . Around 1 g of biomass was pelletised and introduced in the bomb, which was charged with pure oxygen ( 99.99 %) to a pressure of 3.0 ± 0.2 MPa. The bomb had previously been calibrated with benzoic acid.
Two- and three-way ANOVA  with a three-replication design was performed on the data to determine the significance of the following factors: hemp varieties/ nettle treatment V/T: (V/T; for above ground biomass, stems and shives), harvest year Yr: (Yr; for above ground biomass, stems and shives), retting method (R; for shives) on dry matter (DM) yield, C concentration and yield.
2 Features of Carbon Stock in the Biomass of Industrial Hemp and Stinging Nettle 21
2.3 Results and Discussion
According to the data of two-way ANOVA, the DMY both of hemp above-ground biomass (further biomass) and stems, as well as C output in biomass and stems significantly ( P 0.01 or P 0.05) depended on V and did not depend on the growing year (Yr; Table 2.1). Conversely, the effect of the Yr was significant ( P 0.01), and statistically insignificant varietal impact on C concentration (C) in the biomass and stems was revealed. The effect of interaction of the V and Yr on DMY, C yield (CY) as well C in biomass was negligible. Factors’ interaction was significant for C in stems (at P 0.05) only.
Mean biomass DMY per trial amounted to 10607 kg ha− 1 and stems DMY to 9065 kg ha− 1. DMY both of stems and biomass of early-maturing varieties USO 31 and Fedora 17 were significantly lower than mean per trial. One of the most productive varieties was the latest-maturing variety Futura 75. Polish hemp varieties Beniko and Bialobrzeskie were also high yielding though they are ranked as medium early-maturing. The same patterns were obtained regarding CY accumulated in biomass and stems. As C concentration variation with variety was inappreciable DMY was a weighted factor for calculated CY. With regard to the Yr, which is an entireness of environmental conditions of the hemp growth period, lower than average per trial DMY and CY were obtained in 2010 and 2012, in contrast to 2011 where it was higher yielding, though differences from the mean were statistically insignificant. It was observed that hemp biomass, and particularly stems, contained high C concentration (on average 552 and 568 g kg− 1 DM). The highest (at P 0.01) C was found in biomass and stems (558 and 573 g kg− 1 DM) of the 2012 yield, when the lowest average DMY was recorded and vice versa. Some differences in temperature and precipitation distribution during the growing seasons of hemp and plant biomass maturity at harvesting could have an impact on C concentration: The majority of hemp varieties were harvested 2–3 weeks earlier in 2011 than in 2010 and 2012.