The physical and chemical properties of biomass pellets based on wood, willow, miscanthus, wheat, barley and rape straws were each tested using European Committee for Standardisation (CEN) standard ...methods to determine their calorific, ash, chlorine, sulphur, nitrogen, carbon and hydrogen contents as well as durability, bulk density and moisture. In terms of chemical composition, it was found that when compared to wood, willow or miscanthus the straws (i.e. wheat, barley and rape) had higher levels of chlorine, sulphur and nitrogen which could lead to problems in terms of boiler degradation and gaseous emissions. Energy contents of all pellets were very similar with no significant differences between biomass types. The moisture content of wood pellets was significantly lower than the other types of biomass indicating that these raw materials need a higher level of moisture present for binding. While all pellet types had durability levels above 90%, wood was the only pellet to achieve a value above the standard 97.5% level. It was concluded that, the majority of pellet boilers currently on the market are designed specifically for wood pellets and thus, are not capable of adapting to the differing properties of these pellets. The new European standard (EN 14961) fuel specifications give a broad spectrum of quality levels. With improvements in pellet quality through addition of binders and mixtures, developments in boiler design, and with the introduction of new standards, alternative biomass pellets will, in the future, compete favourably with wood pellets for both heat and electricity generation.
► Biomass pellets are compared in terms of their physical and chemical properties. ► The new EN 14961 fuel specifications give a much broader spectrum of quality levels. ► Straws chemical content makes them unsuitable for the majority of pellet boilers. ► Developments in boiler design necessary for future alternative biomass utilisation.
Trials were conducted on four separate but adjacent blocks of willow at a site near Carlow, Ireland in which willow, after one growing season, was either coppiced or left to grow. Each of the four ...randomised complete block design trials contained a different willow genotype (Endeavor, Resolution, Terra nova and Tordis). Coppicing had no adverse effect on stool mortality but significantly increased the number of stems per stool from 2.0 to 3.3. The average, median and maximum diameters of stems from non-coppiced stools were significantly greater than those of stems from coppiced stools. Biomass from non-coppiced treatments was significantly greater than that from coppiced treatments both one year after coppicing (4.3 Mg/ha coppiced; 9.3 Mg/ha non-coppiced) and two years after coppicing (12.6 Mg/ha coppiced; 20.8 Mg/ha non-coppiced). Both coppiced and non-coppiced treatments were harvested two years after coppicing and left to grow for an additional two years. After this two year period, there was no significant difference in stem numbers per stool, stem diameter and biomass yield between the coppiced and non-coppiced treatments. All willow genotypes responded in a similar way to coppicing. The results suggest that the omission of the coppicing operation after one year of growth may increase biomass yield at the first harvest without compromising yield at the second harvest.
•Coppicing had no adverse effect on stool mortality.•Higher yields were obtained from non-coppiced treatments at the first harvest.•No difference in yield between coppiced and non-coppiced treatments at the second harvest.
The natural co-occurrence of 42 mycotoxins was investigated in unprocessed oat grains grown in Ireland. The sample set included a total of 208 oat crops harvested during 2015-2016 and produced using ...conventional, organic, or gluten free farming systems. A range of different toxins was identified, including the major type A (neosolaniol, HT-2 and T-2 toxins, T-2 triol, and T-2-glucoside, co-occurring in 21 samples) and B trichothecenes (deoxynivalenol, nivalenol, and deoxynivalenol-3-glucoside), enniatins (B1, B, and A1, co-occurring in 12 samples), as well as beauvericin, alternariol, mycophenolic acid, and sterigmatocystin. The influences of sowing season, year, and production system were investigated, eventually indicating that the latter factor may have a higher impact than others on the production of certain mycotoxins in oats. The most frequently quantified compounds were HT-2 (51%) and T-2 (41%) toxins, with gluten free oats containing significantly lower concentrations of HT-2 compared to conventionally produced oats. Although the prevalence and concentrations of mycotoxin found in oat samples in this study should be substantially reduced by processing. However, as mycotoxin occurrence is clearly influenced by multiple factors, controlled field trials should be carried out to define optimal agronomic practices and mitigate mycotoxin production. Furthermore, this work highlights the need for regularly testing cereal-based foods with multi-residue analytical methods with wider specificities than the traditionally screened and regulated toxins, to generate knowledge on the occurrence of several mycotoxins that are, to date, rarely investigated.
The potential of near-infrared spectroscopy in conjunction with chemometric techniques to predict the particulate matter and gaseous emissions of biomass pellet blends was assessed in this study. A ...diverse range of biomass was used, including wood, Miscanthus, wheat straw, and the herbaceous energy grass Szarvasi-1 (Elymus elongatus subsp. ponticus cv. Szarvasi-1). The particulate matter emissions were predicted with root-mean-square errors of prediction (RMSEP) of 6.83 (R 2 = 0.57), 8.71 (R 2 = 0.66), and 11.25 (R 2 = 0.65) mg m–3 for the PM10, PM0, and TSP emissions, respectively. The gaseous emissions of oxides of nitrogen (NO x ), sulfur dioxide (SO2), and carbon monoxide (CO) were predicted with RMSEPs of 14.28 (R 2 = 0.93), 4.59 (R 2 = 0.88), and 9.08 (R 2 = 0.48) mg m–3, respectively. No significant models could be developed for the PM2.5 or PM1 emissions. The results indicate that near-infrared spectroscopy has the potential to predict the emissions of biomass pellets in a multibiomass stream.
This paper examines the impact that climate change may have on the lodging of oats in the Republic of Ireland and the UK. Through the consideration of a novel lodging model representing the motion of ...an oat plant due to the interaction of wind and rain and integrating future predictions of wind and rainfall due to climate change, appropriate conclusions have been made. In order to provide meteorological data for the lodging model, wind and rainfall inputs are analysed using 30 years’ time series corresponding to peak lodging months (June and July) from 38 meteorological stations in the United Kingdom and the Irish Republic, which enables the relevant probability density functions (PDFs) to be established. Moreover, climate data for the next six decades in the British Isles produced by UK climate change projections (UKCP18) are analysed, and future wind and rainfall PDFs are obtained. It is observed that the predicted changes likely to occur during the key growing period (June to July) in the next 30 years are in keeping with variations, which can occur due to different husbandry treatments/plant varieties. In addition, the utility of a double exponential function for representing the rainfall probability has been observed with appropriate values for the constants given.
The objective of this study was to compare the fuel-chain greenhouse gas balance and farm economics of hemp grown for bioenergy with two perennial bioenergy crops, Miscanthus and willow, and two more ...traditional annual bioenergy crops, sugar beet and oil seed rape (OSR). The GHG burden of hemp cultivation is intermediate between perennial and traditional annual energy crops, but net fuel chain GHG abatement potential of 11t/CO2 eq./ha/year in the mid yield estimate is comparable to perennial crops, and 140% and 540% greater than for OSR and sugar beet fuel chains, respectively. Gross margins from hemp were considerably lower than for OSR and sugar beet, but exceeded those from Miscanthus when organic fertilizers were used and in the absence of establishment grants for the latter crop. Extrapolated up to the EU scale, replacing 25% of OSR and sugar beet production with hemp production could increase net GHG abatement by up to 21MtCO2eq./year. Hemp is a considerably more efficient bioenergy feedstock than the dominant annual energy crops. Integrated into food crop rotations, hemp need not compete with food supplies, and could provide an appealing option to develop more sustainable non-transport bioenergy supply chains.
► The GHG burden of hemp is intermediate between perennial and annual energy crops. ► Replacing 25% of OSR/beet with hemp could increase GHG abatement by 21Mt/CO2eq./year. ► Hemp is a more efficient bioenergy feedstock than the dominant annual energy crops.
Under natural environment plants experience different light intensities which can affect photosynthesis and consequently the availability of carbohydrates for daytime growth and their transient ...storage to supply night growth. We grew a spring barley cultivar, Propino, under three different light intensities under warm days and nights, and evaluated the spatial and diurnal adjustments occurring in the transient carbon stores. Leaves under high light at the end of the day accumulated mainly sucrose (30%) and malate (35%), with lower content of hexoses (5%), starch (15%) and fructans (15%). Under low light, plants presented reduced photosynthesis, with lower metabolite contents at end of day. The malate represented 51% of the total carbon accumulated at end of the day, at the expense of sucrose (12%), other metabolite contributions remaining similar to high light. The percentage of metabolites consumed at night was similar for all light intensities with around 75% of the sucrose and starch being mobilized whilst malate and fructans were only partially mobilized with 56 and 44%, respectively. Altogether, sucrose and malate were the main contributors of the total carbon used at night by barley plants, sucrose being predominant under high light (35% vs. 27%), but malate being the major metabolite used under low light with 40% of the total carbon consumed. Interestingly, light intensity also influenced the location of the C transient stores, the plants under low light prioritizing the accumulation of the metabolites, mostly malate, in the youngest tissues. Therefore, light influences quantitatively, but also qualitatively and spatially the carbon stores in the spring barley cv. Propino, suggesting a tight regulation of the primary metabolism.
Willow is a fast growing, high yielding biomass crop that can help reduce reliance on fossil fuels. However, long establishment times to get to profitability and sustainable yield may deter interest ...in planting the crop. A number of different approaches were investigated to optimise and accelerate early growth. These approaches were water immersion, plastic application, altering stem orientation at planting, altering coppicing timings and applying growth hormone. Glasshouse and field trials were used to test the different approaches. In this work, planting material was soaked for a varying number of days and plastic was applied or not applied in field trials. In the planting orientation approach, stems were planted diagonally or vertically with half of the planting material above the ground level or horizontally below ground level. Additionally, willow crops were coppiced at different times throughout their first growing season and a growth hormone trial was also incorporated in this work. Water soaking, plastic application, coppicing during the growing season or hormone application did not improve early growth or yield. However, early growth and yield were increased by manipulating the planting orientation of willow stems. Planting orientation treatments in which part of the stem was left above the ground increased early growth and yield significantly compared to the control without requiring extra inputs at planting. The beneficial effects of coppicing can be achieved by manipulating the planting procedure so that the first year’s growth is not disregarded.
Harvesting Miscanthus × giganteus (J.M. Greef & Deuter ex Hodkinson & Renvoize) after shoot emergence is known to reduce yields in subsequent seasons. This research was conducted in Miscanthus to ...assess the effects on crop response and soil compaction of annually repeated traffic, applied both before new growth in the rhizomes (early harvest) and after shoot emergence (late harvest), at two different soil moisture contents. While an annual early harvest, yields more than a late harvest, because damage to new shoots is avoided, soil compaction may be increased following repeated harvests. Five treatments were tested: (a) An untrafficked control, (b) early-traffic on soil with typical soil moisture content (SMC) (early-normal), (c) early-traffic on soil with elevated SMC (early-elevated), (d) late-traffic on soil with typical SMC (late-normal) and (e) late-traffic on soil with elevated SMC (late-wet). The experiment was conducted on a Gleysol in Co. Dublin, Ireland during 2010 and 2011. Crop response effects were assessed by measuring stem numbers, stem height, trafficked zone biomass yield (November) and overall stem yield (January). Compaction effects were assessed by measuring penetration resistance, bulk density and water infiltration rate. Trafficked zone biomass yield in the early-dry and early-wet treatments was, respectively, 18% and 23% lower than in the control, but was, respectively, 39% and 31% higher than in the late-dry treatment. Overall, stem yield was significantly lower in the late-normal and late-wet treatments (10.4 and 10.1 tdm ha−1 respectively) when compared with the control (12.4 tdm ha−1), but no significant difference was recorded in overall stem yield between both early-traffic treatments and the control. Penetration resistance values were significantly higher in all trafficked treatments when compared with the control at depths of 0.15 m (≥54–61%) and 0.30 m (≥27–57%) and were significantly higher in 2011 when compared with 2010 at depths of 0.15 and 0.30 m. Baler system traffic in Miscanthus significantly reduced yields and significantly increased compaction annually. Miscanthus harvested early, on a dry soil, yielded 1.1 tdm ha−1 more than when harvested late on a dry soil. The yield advantage increased to 1.3 tdm ha−1 when early harvesting on a soil with 40–43% moisture content was compared with late harvesting on a wetter soil (51–52% moisture content). In this study, the magnitude of yield losses from compaction or other causes in early harvests was substantially lower than the yield losses, which resulted from shoot damage in late harvests. It is likely in similar climates that the results of this study would also apply to other perennial crops growing in similar soil types.
The results of a study into the precipitation efficiencies of two different electrostatic precipitator (ESP) types (chimney top with manual cleaning and in-line with automated cleaning) using three ...biomass fuels with low (wood), medium (willow) and high (tall fescue) particulate emission levels are presented. Testing showed that precipitation efficiencies of greater than 70% are possible in an inline system with automated cleaning, while in the chimney top, manual cleaning system high efficiencies can be achieved for willow (86%) and wood (69%) on a short term basis. For low emission fuels such as wood (<10 mg Nm−3), acceptable precipitation efficiencies (∼70%) could be achieved and maintained over a long time period on both automated and manual systems. For medium (willow > 100 mg Nm−3) and high (tall fescue > 300 mg Nm−3) emission fuels it was found that the use of an automated cleaning system is necessary to maintain precipitation efficiencies at acceptable levels. In the chimney top type, system efficiencies dropped to zero with willow after 50 h and with tall fescue after 10 h of combustion with no cleaning, due to build-up of particulate matter on the electrode causing reduced distribution of charge to the oncoming particles. For the in-line system, it was also shown that an improved electrode design had the capacity to increase precipitation efficiency by on average 18%. It was concluded that ESPs have an important role to play in particulate emission reduction in future low emission biomass combustion systems if they are to meet stricter particulate control guidelines.
•Two ESP types were tested and compared for particulate precipitation efficiency.•Efficiencies >70% achieved for both types for all fuels but this reduces over time.•Fuels with high particulate emissions need automatic cleaning.•ESPs have important role to play in reducing particle emissions for new guidelines.
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