Carbohydrate composition in delayed harvested reed canary grass

Reed canary grass (Phalaris arundinacea L.) samples of the Palaton variety grown at 10 different locations in northern Europe were analyzed and the effect of growing location and soil type on the carbohydrate composition and lignin content were investigated. The results showed that the major carbohydrate components in delayed harvested reed canary grass were glucose and xylose. Some growing locations and soil types significantly influenced the carbohydrate composition of the grass. Soils with both high organic and clay content produced lower glucose and xylose contents but an increased lignin content. A soil rich in sand gave higher glucose, xylose and arabinose content.Reed canary grass is a perennial rhizome grass that has shown potential as an energy crop for solid bio-fuel production and as a short fibre raw material for the pulp and paper industry. This study showed that delayed harvested reed canary grass can also be a potential new raw material for ethanol production.     

Energy efficient pilot-scale production of wood fuel pellets made from a raw material mix including sawdust and rapeseed cake

Presently, most fuel pellets are made from sawdust or shavings. In Sweden, these materials are used to the maximum extent. As the demand for pellets increases, the supply of sawdust will be insufficient and other raw materials or mixes of raw materials will be used. This work investigates sawdust mixed with rapeseed cake. The latter is a residual product from the production of chemically unmodified oil refined from cold-pressed rape oil. At the Department of Energy, Environmental and Building Technology at Karlstad University, Sweden, a complete pilot-scale pellet production unit is located. The pellets are produced and tested for mechanical durability, length, bulk density and moisture content according to the Swedish Standard for pellets. During production, the load current, the die pressure and the die temperature were measured along with other parameters. The main purpose was to examine how the mixture of rapeseed cake and pine sawdust affected the energy consumption of the pelletising machine and mechanical durability of mixed fuel pellets. The results show that the energy consumption decreased and the amount of fines increased with increasing rapeseed cake in the wood fuel pellets. These results indicate that we must compromise between a decrease in the use of energy and a decrease in durability.     

Biorefining of agricultural crops and residues: Effect of pilot-plant fractionation on properties of fibrous fractions

Bio-refining in this work consists of the production of chip (fibre) and meal fractions from winter wheat (Triticum sativum) straw and oilseed rape (Brassica napus) straw, canary reed (Phalaris arundinacea) and miscanthus (Miscanthus sinensis) in a 1 t h⁻¹ capacity pilot plant. Chip fractions were evaluated as raw materials for fibre and pulp production following delignification using aqueous NaOH (0.25–2.5N) at 100–150°C for 60–180 min, with a solid-to-liquid ratio of 1:10 (w/v). Miscanthus and winter wheat straw were fractionated to give high chip yields (66–70%). The introduction of a biorefining step was found to be justified in the case of winter wheat straw and canary reed due to positive effects on pulp yield and mechanical properties. Meal fractions were also enriched in protein by this process.     

Greenhouse gas balances of transportation biofuels,electricity and heat generation in Finland—Dealing with the uncertainties

One way to reduce greenhouse gas emissions from the transportation sector is to replace fossil fuels by biofuels. However, production of biofuels also generates greenhouse gas emissions. Energy and greenhouse gas balances of transportation biofuels suitable for large-scale production in Finland have been assessed in this paper. In addition, the use of raw materials in electricity and/or heat production has been considered. The overall auxiliary energy input per energy content of fuel in biofuel production was 3–5-fold compared to that of fossil fuels. The results indicated that greenhouse gas emissions from the production and use of barley-based ethanol or biodiesel from turnip rape are very probably higher compared to fossil fuels. Second generation biofuels produced using forestry residues or reed canary grass as raw materials seem to be more favourable in reducing greenhouse gas emissions. However, the use of raw materials in electricity and/or heat production is even more favourable. Significant uncertainties are involved in the results mainly due to the uncertainty of N₂O emissions from fertilisation and emissions from the production of the electricity consumed or replaced.     

Reed canary grass yield and fuel quality in Estonian farmers’ fields

Reed canary grass (Phalaris arundinacea) is one of the possible raw materials for bioenergy production in northern Europe. Its cultivation is favoured because its high productivity and local origin. However, problems with the biomass quality for combustion have been reported. Usually delayed harvest in spring is suggested to improve the quality and decrease the moisture content of biomass. On the other hand, the feasibility of spring harvest depends on local climatic conditions and may cause yield losses. In current paper we studied reed canary grass fields in Estonia locating on different soil types and cultivated with various varieties. The influence of several fertilisation schemes on biomass yield was analysed. Our results indicated that production was higher on mineral soils than on the organic soil of abandoned peat extraction sites. Even different types of fertilisation did not increase the production on organic soils to the level comparable to those on mineral soils. Among studied varieties ‘Venture’ had the highest production. The highest yield per area was obtained late in the autumn (12.7 t d.w. per ha and 7.2 t d.w. per ha on mineral and organic soils, respectively). By spring the amount of biomass had decreased in all studied sites. Due to wet soil some of the fields remained unharvested, the others had high yield losses during practical harvesting. The chemical analyses did not reveal significant differences in the composition of biomass between late autumn and spring. Therefore we conclude that late autumn harvest should be preferred in local climatic conditions.     

Quality properties of pelletised sawdust,logging residues and bark

The dominant raw material for wood pellet production in Sweden is sawdust, planer shavings and dry chips. However, other types of biomass, such as bark and logging residues, are also interesting raw materials due to the large volumes available. These alternative raw materials differ from stemwood with regard to physical characteristics and chemical composition. In order to produce high-quality pellets of such materials, it is necessary to understand the role of these variations. Nine pellet assortments, made of fresh and stored sawdust, bark and logging residues (a mixture of Norway spruce and Scots pine) were tested for moisture content, heating value and contents of ash, sulphur, chlorine and Klason lignin. Dimensions, bulk density, density of individual pellets, durability and sintering risk were also determined. The heating value was highest in logging residue pellets. The ash content was highest in the bark and logging residue pellets, implying higher sintering risk compared with sawdust pellets. The results showed that bark pellets had the highest durability, whereas sawdust pellets had the lowest. Pellet density had no effect on durability, unlike lignin content which was positively correlated. It is concluded that bark and logging residues are suitable raw materials for pellets production, especially if the ash content is controlled.     

Reed canary grass transportation costs – Reducing costs and increasing feasible transportation distances

Reed canary grass is used in several heat and power plants in Finland and it is estimated that about 70–80 plants could utilise reed canary grass as a co-firing fuel. Long-distance transport of reed canary grass forms a significant share of the production and delivery costs. Reed canary grass can be transported in bales or as loose matter. The density of the matter and shape of the bales influence the load-size and the cost. At present it is impossible to obtain the full load-bearing capacity of a lorry even with bales, and with light bulk matter the obtainable load is less than one-third of the load-bearing capacity of a lorry. By using Orkel local-baler it has been possible to obtain the largest load-sizes, but the total economy of the chain is not very good because the baling and chopping of bales increase the total costs. If a full load-bearing capacity of a lorry (30–40 tonne) would be obtained, the transportation costs would be reduced significantly compared to the present situation. Second alternative would be to mix reed canary grass with wood chips or peat before long-distance transport. At the moment feasible transportation distances are relatively short. With briquettes the cargo space could be used more efficiently and the load-size of the transport could be increased.     

Evaluation of the performance of a multi-fuel domestic boiler with respect to the existing European standard and quality labels: Part-1

Emissions from a multi-fuel domestic boiler (40 kW), fired with nine different agro-biomass pellets have been compared. The pellets include apple pomace (Malus domestica), reed canary grass (Phalaris arundinacea), pectin waste from citrus shells (Citrus reticulata), sunflower husk (Helianthus annuus), peat, two types of straw pellets and two types of wood pellets. The measurements of emissions comprised carbon monoxide (CO), nitrogen oxides (NO_x), unburned hydrocarbons (C_xH_y), sulphur oxides (SO_x) and flue dust mass concentration (by DINplus and isokinetic sampling methods). Comparison of experimental emission values with relevant quality labels (Blue Angel and Swan Mark) and standard (EN-303-5) showed that the boiler satisfied the emissions requirements of Blue Angel, Swan Mark and EN-303-5 when using wood pellets-1 (except CO emission), reed canary grass and citrus pectin waste pellets as fuel at nominal load. The wood pellets-1 yielded the highest boiler efficiency of 92.4%. Dusts emission varied as a function of fine content and elemental constituent of the pellets and was the highest with sunflower husk. CO and C_xH_y emissions were maximum with peat pellets. NO_x emissions were below the concerned permissible values with all experimental pellets. Emissions of NO_x and SO_x were found maximum with straw pellets.For agro-pellets, statistical differences in ash contents were significant. High ash contents and low ash melting temperature made straw pellets less suitable for domestic applications. Reed canary grass, citrus pectin and apple pellets were the most suitable agro-pellets for small scale boilers with reasonable less ash contents and less emissions as compared to others.     

Environmental effects of energy crop cultivation in Sweden—II: Economic valuation

In this paper, environmental benefits of the cultivation of perennial energy crops in Sweden, which have been identified and quantified in an earlier paper, are evaluated economically. Several different benefits, ranging from global to site-specific, could be achieved by replacing annual food crops with perennial energy crops. The economic value of these environmental benefits, including reductions in costs to farmers (direct costs) and to society as a whole (external costs), has been estimated to be from US$ 0.1 up to US$ 5/GJ biomass. For comparison, the production costs (excluding transport) of Salix and reed canary grass are about 4.4 and US$ 5.0/GJ, respectively. Purification of waste water in energy crop cultivation has the highest economic value, followed by reduced nutrient leaching through riparian buffer strips, recirculation of sewage sludge, and reduced wind erosion through shelter belts consisting of Salix. The value of other environmental benefits is estimated to be less than US$ 0.7/GJ. If 200,000 ha of Sweden’s totally available arable land of 2.8 Mha were available for energy crop cultivation, around 45 PJ biomass could theoretically be produced per year, at an average cost of about US$ 0.7/GJ, including the value of environmental benefits. It is assumed that priority is given to cultivations with the highest total value, as several different environmental effects could be achieved on the same cultivation site. If 800,000 ha were to be available, the corresponding cost of some 150 GJ biomass per year would be around US$ 2.8/GJ.     

Wood pellets production costs and energy consumption under different framework conditions in Northeast Argentina

The development of cleaner and renewable energy sources are needed in order to reduce dependency and global warming. Wood pellets are a clean renewable fuel and has been considered as one of the substitutes for fossil fuels. In Argentina, large quantities of sawmill residues are still unused and wood pellets production could be seen as both, as an environmental solution and an extra economical benefit. The general aim of this study was to determine the wood pellets production costs and energy consumption under different framework conditions in northeast Argentina. The specific costs of wood pellets for the different scenarios showed relative lower costs comparing to the ones reported in other studies, ranging from 35 to 47 €/Mg_pellets. Raw material costs represented the main cost factor in the calculation of the total pellets production costs. A lower specific production cost was observed when 50% of the raw material input was wood shavings. The specific electricity consumption per metric ton of pellet was lower in scenarios with higher production rate. Lower heat energy consumption was observed in scenarios that have a mixed raw material input. The most promising framework condition for Northeast Argentina, in terms of costs effectiveness and energy consumption could be acquired with production rates of 6 Mg/h with sawdust and wood shavings as raw material. However, simultaneous increment of the electricity by 50% and raw material price by 100% may increase the specific costs up to 50%.     

Environmental effects of energy crop cultivation in Sweden—I: Identification and quantification

This paper presents an analysis of how energy crop cultivations in Sweden, consisting of short-rotation forest (Salix) and energy grass (reed canary grass), can be located and managed to maximise environmental benefits. The overall conclusion is that substantial environmental benefits, ranging from global to site-specific, could be achieved when traditional annual food crops produced with current agriculture practices are replaced by dedicated perennial energy crops. The emission of greenhouse gases could be reduced by reduced carbon dioxide emissions from organic soils, by reduced nitrous oxide emissions caused by the use of fertilisers and through accumulation of soil carbon in mineral soils, which also leads to increased soil fertility. Nutrient leaching could be reduced by using energy crop cultivations as buffer strips along open streams and wind erosion could be reduced by using Salix plantations as shelter belts. Cultivation of Salix and energy grass can also be used to purify municipal waste, such as waste water, landfill leachate, and sewage sludge. Furthermore, the content of heavy metals in the soil can be reduced through Salix cultivation. The biodiversity is estimated to be almost unchanged, or slightly increased in open farmland. These environmental benefits, which could be achieved on up to 60% of current Swedish arable land and last for 25 years or more, will increase the value of the energy crops. The economic value of these benefits is calculated in Part II of the analysis, which is presented in a second paper.     

Influence of various machinery combinations,fuel proportions and storage capacities on costs for co-handling of straw and reed canary grass to district heating plants

Autumn-harvested cereal straw and spring-harvested reed canary grass (Phalaris arundinacea L.) are renewable energy sources with similar material characteristics. The fuels can be harvested and handled with the same machines, stored in the same stores, and fired with the same equipment. Thus, there is a possibility to reduce costs and increase supply reliability at many locations by using reed canary grass (RCG) as a complementary fuel in straw-fired district heating plants. The objective of this study was to find appropriate machinery combinations, straw/RCG proportions and storage capacities in order to reduce the total costs of the fuel system. The tool for the analyses was a modified dynamic simulation model for straw handling called SHAM (Straw HAndling Model). To include handling of RCG, SHAM was extended with submodules for calculation of daily fuel use, soil moisture contents and early crop growth. The model was applied to a fictitious heating plant in Enköping in central Sweden as a case study. The simulations showed that the total costs can be lowered by using both straw and RCG in suitable proportions instead of solely using straw, although the primary fuel cost for RCG is more than three times higher per GJ than for straw. The choice of reserve base load fuel had a significant impact on the results, particularly when the RCG proportion was small, because the consumption of the reserve fuel became proportionally higher in such cases.     

Performance of a domestic pellet boiler as a function of operational loads: Part-2

Emissions and efficiency of a pellet boiler (40 kW) at nominal load were compared with emissions and efficiency at reduced load, while fired with six biomass pellets. The pellets include reed canary grass (Phalaris arundinacea), pectin waste from citrus shells (Citrus reticulata), sunflower husk (Helianthus annuus), peat, wheat straw (Triticum aestivum) and wood pellets. The measurements of emissions comprised of carbon monoxide (CO), nitrogen oxides (NO_x), sulphur oxides (SO_x) and flue dust mass concentrations (using DINplus and isokinetic sampling techniques). Emissions varied as a function of operational loads, for each type of pellets.The CO emissions were insignificant with reed canary grass (RCG), citrus pectin waste (CPW) and straw pellets at nominal load, however, at reduced load same pellets emitted 1.9, 4.0 and 7.4 times higher CO than wood pellets, respectively. Peat pellets emitted maximum CO at nominal load (4221.1 mgNm⁻³, 12.6 times higher than wood pellets) however; at reduced load CO emission was insignificant. The highest NO_x emissions were reported with CPW, which were 3.4 and 4.6 times higher than wood pellets at nominal load and reduced load, respectively. Dust emissions were highest with sunflower husk and lowest with RCG pellets, at both operational modes. The best performance was reported with wood pellets, followed by RCG and pectin pellets, however, wood pellets combustion emitted 1.7 and 2.0 times higher dust_DINplus than RCG at nominal and reduced loads, respectively. Not only fuel specific combustion optimization but also operational load specific optimization is essential for efficient use of agro-pellets in this type of boilers.     

New opportunities for the exploitation of energy crops by thermochemical conversion in Northern Europe and the UK

Currently, significant academic and industrial activity is focused on sourcing feed stocks from non-food biomass crops for the sustainable production of energy, power and chemical products. Crops identified as suitable for Northern Europe include Miscanthus, switchgrass (Panicum virgatum), reed canary grass (Phalaris arundinacea) and short rotation coppice willow and poplar (Salix and Populus spp.). All of these crops provide biomass that is amenable for conversion by thermochemical processes i.e. those based on heat and pressure. There are concerns that for some processes the conversion efficiency of biomass is poor compared with coal and oil due to comparatively low energy density, high moisture content, and poor storage and handling properties. Many of these parameters can be improved by pre-processing feed stock materials prior to their conversion. We examine the energy crop species that are suitable for Northern Europe; discuss the processes of combustion, gasification and pyrolysis, and explore how differences in chemical composition influence conversion efficiency. Finally, we review biomass upgrading (pelletisation, torrefaction and treatment with sub-critical (hydrothermal upgrading) and with supercritical water).     

Assessment of the energetic and mechanical properties of pellets produced from agricultural biomass

This paper presents an assessment of the energetic and mechanical properties of pellets produced from agricultural biomass. For the production of pellets the following raw materials were used: wheat straw, rape straw, and maize straw. Additionally, the mixtures of wheat-rape straw, wheat-maize straw, and rape-maize straw (each accounting for 50% of the mass) were applied. The studied resources were ground with the use of a universal shredder driven by a 7.5 kW electric engine. A pelleting machine fitted with a fixed flat matrix with two driven thickening rolls was used to produce the pellets. Analyses of the moisture and calorific value of resources as well as the bulk density and mechanical strength of pellets were performed according to biding standards. The moisture of resources ranged from 16.5% to 18.5% for rape and maize straw, respectively. The average calorific value fluctuated between 15.3 MJ kg⁻¹ for a mixture of wheat and rape straw to 16.2 MJ kg⁻¹ for maize straw. The bulk density and mechanical strength of pellets depended on the type of resources used. The lowest bulk density was recorded for wheat straw pellets (386–420 kg m⁻³), and the highest (561–572 kg m⁻³) for maize straw pellets. The lowest mechanical strength of pellets was noted for rape (95.4–96.8%), whereas the highest was for pellets made from a wheat and maize straw mixture (96.8–98.9%).     

Effect of raw material composition in woody biomass pellets on combustion characteristics

Char yield, char combustion time and char combustion rate of pellets made from different tree parts of Norway spruce and industrially made stem wood pellets of Norway spruce and Scots pine were studied. The pellets were incinerated in a laboratory scale oven at various temperatures, gas flows and oxygen concentrations.It was found that the combustion time for a single pellet mostly depended on the raw material composition and to a minor extent on the density. Pellets made of bark had up to a 50% longer char combustion time compared to that of stem wood pellets, due to differences in char yield. Industrially made stem wood pellets of pine and spruce sawdust were found to have small differences in combustion characteristics. The variations in combustion characteristics of pellets are discussed in relation to composition of raw material.     

Hydrothermal carbonization of distiller’s grains

Wet distiller’s grains are intermediate byproducts of ethanol manufacture that have high moisture contents and require significant energy for drying and conversion into dry distiller’s grains. Hydrothermal carbonization was investigated as a wet process to provide alternative products, and chars were obtained in moderate yield that possessed high heats of combustion. The mechanism of char formation was also investigated employing constituent materials representative of the chemical composition of distiller’s grains. Char formation was discovered to chiefly involve carbohydrates (other than cellulose) and proteins. A surprising discovery was that triacylglycerides and fatty acids created under the reaction conditions did not contribute to char yield and were adsorbed onto the chars and could be easily extracted.     

Biogenic hydrogen and methane production from reed canary grass

The composition, biodegradability, abundance, availability and cost determine the amenability of carbonaceous substrate for fermentative hydrogen and methane production systems. The aim of the present work was to determine suitability of lignocellulosic material, reed canary grass (RCG) (Phalaris arundinacea L.), for hydrogen and methane production at 35 °C by utilizing solid RCG and acid hydrolyzed soluble RCG. Synthetic cellulose was used as control substrate. Acid hydrolysis released 61.7 mg g⁻¹ (dw) and 115 mg g⁻¹ (dw) of reducing sugars from synthetic cellulose and chopped RCG, respectively. More hydrogen was produced from acid hydrolyzed RCG than from solid RCG, the highest yield being 1.25 mmol H₂ per g (dw) RCG. Methane production from solid RCG resulted in the highest yield of 8.26 mmol CH₄ per g (dw) RCG. In summary hydrogen and methane was produced from RCG, and acid hydrolysis was required for hydrogen, but not for methane production.     

The effect of bark content on quality parameters of Scots pine (Pinus sylvestris L.) pellets

Increased use of pellets has resulted in a shortage of the traditional raw materials required for pellet making, including saw dust, shavings and cuttings from saw mills. Therefore, the pellets industry has started to look for alternative raw materials. Limited consumption of pulpwood from Scots pine (Pinus sylvestris L.) in Norway has made it a potential raw material for the pellets industry.A study on how bark content affects the quality of pellets is reported in this paper. Pellets from pinewood containing zero, five, 10, 30 and 100 percent bark were produced, and their quality parameters were evaluated. Combustion tests were also performed on the produced pellets.Pellets made from pure bark had the best mechanical properties compared with pellets made of wood containing various concentrations of bark. The differences were not substantial and the durability for all chosen assortments was in the same quality class in the CEN standard. A positive effect off the amount of steam added was found. The bulk densities of the blend pellets were higher than those of pure wood and bark. The ash content increased with the amount of bark in the pellets. There were no problems with sintering when the bark content was low (five and 10 percent). For pure bark pellets some sintering was registered.     

Planning land use for biogas energy crop production: The potential of cutaway peat production lands

Each year, thousands of hectares of peatland that had been harvested are being released in Finland, which can offer an opportunity to increase energy crops and attain the bioenergy targets for non-agriculture lands. In this study, the Geographic Information System (GIS) method was used to improve the assessment of decentralized renewable energy resources. The amount of peat production lands and future cutaway areas for energy crop production was calculated as a case study by using ArcGIS and the Finnish Topographic database. There are almost 1000 km² of peat production lands in Finland, and theoretically, approximately 300 km² of cutaway peatlands could be used for energy crops after 30 years. The dry biomass yield of reed canary grass (Phalaris arundinacea) or timothy-fescue grass (mix of Phleum pratense and Festuca pratensis) could be higher than 100 Gg a⁻¹ in these lands indicating methane potential of approximately 300 GWh. The exhausted peat production areas in the western region of Finland have significant potential for use for energy crops; North and South Ostrobothnia account for almost 45% of the total peat production land. A future goal could be to use the cutaway peat production lands more efficiently for bioenergy to mitigate climate change. Since the use of wastelands (including peatlands) are being considered in Europe as a way to avoid competition with food production, the GIS method used in the study to identify suitable peat lands could be applicable to biomass resource studies being conducted in many countries.