Virginia mallow (Sida hermaphrodita (L.) Rusby) as perennial multipurpose crop: biomass yields,energetic valorization,utilization potentials,and management perspectives

This article reviews the scholarly literature dealing with the perennial multipurpose crop Virginia mallow (Sida hermaphrodita (L.) Rusby; Sida in the following). In regions dominated by intensive agricultural management practices, growing Sida holds the potential to combine ecosystem services such as decreasing soil erosion, reducing nitrate leaching as well as enhancing biodiversity, with economic profit for the farmer. After promising biomass yields of Sida were reported from studies performed in Poland about 15 years ago, the interest in this plant species has continuously increased, and different utilization pathways were examined, predominantly by researchers in Poland and Germany. At present, however, a comprehensive overview that summarizes the different lines of research performed regarding the use of Sida is lacking. This review aims at closing this gap. After providing background information on Sida, we summarize the main results obtained from investigations concerning biomass yields, fertilization effects, key findings concerning direct combustion, biogas production, steam gasification, phytoremediation, and alternative utilization pathways. Thereafter, we highlight important aspects of Virginia mallow cultivation practices, including first estimates regarding the costs involved. Finally, we point to existing research gaps. Summarizing the available literature on Sida, we aim at raising the interest of scientists and farmers in this plant species further and to show where future research might tie in with, as the successful cultivation of Sida might represent a worthwhile strategy to transform current agricultural practices in Central Europe into approaches that are more sustainable and resilient against future challenges.     

Combustion of horse manure for heat production

The main objectives of this paper have been to evaluate the use of horse manure and wood-shavings as a fuel for heat production and to provide sets of data on the chemical composition, ash characteristics and ash forming elements of the fuel. Another objective has been to investigate the possibility to use the ash as fertiliser by analysing the heavy metal and nutrient contents. The results showed that the fuel is well suited for combustion for heat production causing low emissions of products of incomplete combustion. The emissions of NO_x were however high due to the high content of fuel bound nitrogen. Emissions of CO and NO_x were typically in the range of 30–150 mg/Nm³ and 280–350 mg/Nm³ at 10 vol% O₂, respectively. The analysis of the ash showed on sufficiently low concentration of heavy metals to allow recycling.     

Miscanthus for biogas production: Influence of harvest date and ensiling on digestibility and methane hectare yield

The 8,000 biogas plants currently in operation in Germany are mainly fed with biomass from annual crops. However, feedstock from perennial crops such as miscanthus is expected to be more environmentally benign. If miscanthus is to be used in greater amounts as a substrate for anaerobic digestion, storage will become a relevant topic, as a continuous supply of biomass throughout the year is necessary. The objective of this study was to identify the miscanthus harvest time that best balances the simultaneous achievement of high silage quality, high digestibility and high methane hectare yields. For this purpose, biomass from four miscanthus genotypes with varying senescence characteristics was harvested on three different dates in autumn 2017. Part of the biomass was ensiled, and the methane yield of both ensiled and non‐ensiled biomass was analysed in a biogas batch test to assess the effect of ensiling on the methane hectare yield and digestion velocity. The ensiled biomass was found to have an up to 7% higher substrate‐specific methane yield and also showed a higher digestion velocity than the non‐ensiled biomass. The silage quality was best when miscanthus was harvested in mid‐October, due to highest lactic acid content (average: 3.0% of DM) and lowest pH (average: 4.39) compared to the harvests in mid‐September and beginning of October. Mass losses during ensiling (as high as 7.6% of fresh matter for the M. sinensis genotype Sin55) were compensated for by a higher substrate‐specific methane yield (up to 353 Nml CH₄ (g oDM)^?1) in ensiled miscanthus. This resulted in non‐significantly different methane hectare yields for non‐ensiled (average: 4.635 Nm³ CH₄/ha) and ensiled miscanthus biomass (4.803 Nm³ CH₄/ha). A comparison of the four genotypes suggests that Miscanthus x giganteus is the most suitable genotype for ensiling as it had the best silage quality.     

Emission and Control Characteristics for Incineration of Sedum Plumbizincicola Biomass in a Laboratory-Scale Entrained Flow Tube Furnace

Experiments were conducted to investigate and control pollutant emission from incineration of Sedum plumbizincicola plants on a laboratory scale using an entrained flow tube furnace. Without control technologies, the flue gas contained 0.101 mg Nm^?3 of Cd, 46.4 mg Nm^?3 of Zn, 553 mg Nm^?3 of NOx, 131 pg Nm^?3 of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/Fs) and 35.4 mg Nm^?3 of polycyclic aromatic hydrocarbons (PAHs). In pollutants control experiments. Al₂O₃, CaO, and kaolin were compared as adsorbents and activated carbon was used as an end-of-pipe method for the capture of pollutants. Kaolin, the most effective of the three adsorbents, removed 91.2% of the Cd in flue gas. While 97.6% of the Cd and 99.6% of the PAHs were removed by activated carbon. Incineration may therefore be regarded as a viable option for the safe disposal of the biomass of the zinc and cadmium hyperaccumulator species S. plumbizincicola.     

Energetics of Acidianus ambivalens growth in response to oxygen availability

All life requires energy to drive metabolic reactions such as growth and cell maintenance; therefore, fluctuations in energy availability can alter microbial activity. There is a gap in our knowledge concerning how energy availability affects the growth of extreme chemolithoautotrophs. Toward this end, we investigated the growth of thermoacidophile Acidianus ambivalens during sulfur oxidation under aerobic to microaerophilic conditions. Calorimetry was used to measure enthalpy (ΔH_inc) of microbial activity, and chemical changes in growth media were measured to calculate Gibbs energy change (ΔG_inc) during incubation. In all experiments, Gibbs energy was primarily dissipated through the release of heat, which suggests enthalpy‐driven growth. In microaerophilic conditions, growth was significantly more efficient in terms of biomass yield (defined as C‐mol biomass per mole sulfur consumed) and resulted in lower ΔG_inc and ΔH_inc. ΔG_inc in oxygen‐limited (OL) and oxygen‐ and CO₂‐limited (OCL) microaerophilic growth conditions resulted in averages of ?1.44 × 10³ kJ/C‐mol and ?7.56 × 10² kJ/C‐mol, respectively, and average ΔH_inc values of ?1.11 × 10⁵ kJ/C‐mol and ?4.43 × 10⁴ kJ/C‐mol, respectively. High‐oxygen experiments resulted in lower biomass yield values, an increase in ΔG_inc to ?1.71 × 10⁴ kJ/C‐mol, and more exothermic ΔH_inc values of ?4.71 × 10⁵ kJ/C‐mol. The observed inefficiency in high‐oxygen conditions may suggest larger maintenance energy demands due to oxidative stresses and a preference for growth in microaerophilic environments.     

Diverting residual biomass to energy use: Quantifying the global warming potential of biogenic CO2 (GWPbCO2)

To calculate the global warming potential of biogenic carbon dioxide emissions (GWP_bCO2) associated with diverting residual biomass to bioenergy use, the decay of annual biogenic carbon pulses into the atmosphere over 100 years was compared between biomass use for energy and its business-as-usual decomposition in agricultural, forestry, or landfill sites. Bioenergy use increased atmospheric CO₂ load in all cases, resulting in a ¹⁰⁰GWP_bCO2 (units of g CO₂e/g biomass CO₂ released) of 0.003 for the fast-decomposing agricultural residues to 0.029 for the slow, 0.084–0.625 for forest residues, and 0.368–0.975 for landfill lignocellulosic biomass. In comparison, carbon emissions from fossil fuels have a ¹⁰⁰GWP of 1.0 g (CO₂e/g fossil CO₂). The fast decomposition rate and the corresponding low ¹⁰⁰GWP_bCO2 values of agricultural residues make them a more climate-friendly feedstock for bioenergy production relative to forest residues and landfill lignocellulosic biomass. This study shows that CO₂ released from the combustion of bioenergy or biofuels made from residual biomass has a greenhouse gas footprint that should be considered in assessing climate impacts.     

Biogas production from different substrates in an experimental Continuously Stirred Tank Reactor anaerobic digester

Different mixtures were digested in a single-stage, batch, mixed, laboratory scale mesophilic anaerobic digester at the Biomass Research Centre Laboratory (University of Perugia). The yield and the composition of biogas from the different substrates were evaluated and the cumulative curves were estimated. Two experimental campaigns were carried out, the first on three mixtures (chicken, pig and bovine manures), the second on animal and vegetal biomasses (chicken and cow manure, olive husk) with different inocula (rumen fluid and digested sludge). In the first campaign pig manure mixture showed the maximum biogas production (0.35 Nm³/kg) and energy content (1.35 kWh/kg VS); in the second one the differences in produced biogas from the different inocula were analyzed: olive husk with piggery manure anaerobically digested as inoculum showed the higher biogas (0.28 Nm³/kg VS) and methane yield (0.11 Nm³/kg VS), corresponding to an energetic content of 1.07 kWh/kg VS. All data obtained from the laboratory scale anaerobic digester are comparable to the values in literature for several biomass and in particular for olive husk, dairy manure and chicken manure.     

Phytoextraction of heavy metals from municipal sewage sludge by Rosa multiflora and Sida hermaphrodita

The aim of the study was to evaluate the efficacy of the multiflora rose var. “Jatar” (Rosa multiflora Thunb. ex Murray) and the Virginia fanpetals (Sida hermaphrodita Rusby) to phytoextract heavy metals from municipal sewage sludge. The 6-year field experiment involved four levels of fertilization with sewage sludge at doses of 0, 10, 20, 40, and 60 Mg DM (Dry Mass) sludge ha^?1. The increasing doses of sewage sludge were found to significantly increase the yield of multiflora rose and Virginia fanpetals biomass. They also significantly increased the content of heavy metals in these plants. The highest uptake of heavy metals by the multiflora rose and Virginia fanpetals crops was recorded at the fertilization dose of 60 Mg DM ? ha^?1. Our investigations show that the Virginia fanpetals was more efficient in the phytoextraction of Cr, Ni, Cu, Zn, and Cd from the sewage sludge than the multiflora rose, due to the greater yields and higher heavy metal uptake by the former plant. In turn, the multiflora rose phytoextracted greater amounts of Pb from the sewage sludge. The analyses indicate that the Virginia fanpetals can be used for phytoremediation (phytoextraction) of heavy metals contained in sewage sludge.     

Continuous biomethanization of agrifood industry waste: A case study in Spain

The anaerobic digestion technology is a biological treatment widely used to reduce the pollution load of wet waste biomass. In this work we present the results obtained by performing extensive experiments of anaerobic digestion of slaughterhouse waste, tomato industry waste and olive oil industry waste in continuous mode, which were designed to demonstrate that anaerobic digestion is an effective technology from an environmental and economic point of view.Biogas yields obtained are between 35.22 and 5.45 Nm³ biogas/m³ olive oil industry waste and tomato industry waste respectively and the slaughterhouse wastes achieve intermediate production, 30.86 Nm³ biogas/m³ municipal slaughterhouse waste and 22.53 Nm³ biogas/m³ Iberian pig slaughterhouse waste. Moreover, it possible to degrade between 63.46 and 75.3% of the initial organic matter.If these results are analyzed, the environmental, energetic economic benefits of anaerobic digestion can be quantified. Biomethanation of all these wastes generated annually in Extremadura could prevent the emission of 134,772 t of equivalent carbon dioxide, generate an energy similar to that provided by 2826 toe and reach payback times from 3.29 to 3.75 years for anaerobic digestion plant designed to treat the wastes generated by a medium-sized industry. So, we have fulfilled all the planned aims.     

The climate change mitigation effect of bioenergy from sustainably managed forests in Central Europe

We compare sustainably managed with unmanaged forests in terms of their contribution to climate change mitigation based on published data. For sustainably managed forests, accounting of carbon (C) storage based on ecosystem biomass and products as required by the United Nations Framework Convention on Climate Change is not sufficient to quantify their contribution to climate change mitigation. The ultimate value of biomass is its use for biomaterials and bioenergy. Taking Germany as an example, we show that the average removals of wood from managed forests are higher than stated by official reports, ranging between 56 and 86 mill. m³ year^?1 due to the unrecorded harvest of firewood. We find that removals from one hectare can substitute 0.87 m³ ha^?1 year^?1 of diesel, or 7.4 MWh ha^?1 year^?1, taking into account the unrecorded firewood, the use of fuel for harvesting and processing, and the efficiency of energy conversion. Energy substitution ranges between 1.9 and 2.2 t CO_{2 equiv.} ha^?1 year^?1 depending on the type of fossil fuel production. Including bioenergy and carbon storage, the total mitigation effect of managed forest ranges between 3.2 and 3.5 t CO_{2 equiv.} ha^?1 year^?1. This is more than previously reported because of the full accounting of bioenergy. Unmanaged nature conservation forests contribute via C storage only about 0.37 t CO_{2 equiv.}  ha^?1 year^?1 to climate change mitigation. There is no fossil fuel substitution. Therefore, taking forests out of management reduces climate change mitigation benefits substantially. There should be a mitigation cost for taking forest out of management in Central Europe. Since the energy sector is rewarded for the climate benefits of bioenergy, and not the forest sector, we propose that a CO₂ tax is used to award the contribution of forest management to fossil fuel substitution and climate change mitigation. This would stimulate the production of wood for products and energy substitution.     

Biomass production and energy balance of Miscanthus over a period of 11 years: A case study in a large‐scale farm in Poland

Giant miscanthus (Miscanthus × giganteus Greef and Deuter) and Amur silver grass (Miscanthus sacchariflorus Maxim./Hack) are rhizomatous grasses with a C4 photosynthetic pathway that are widely cultivated as energy crops. For those species to be successfully used in bioenergy generation, their yields have to be maintained at a high level in the long term. The biomass yield (fresh and dry matter [DM] yield) and energy efficiency (energy inputs, energy output, energy gain, and energy efficiency ratio) of giant miscanthus and Amur silver grass were compared in a field experiment conducted in 2007–2017 in North‐Eastern Poland. Both species were characterized by high above‐ground biomass yields, and the productive performance of M. × giganteus was higher in comparison with M. sacchariflorus (15.5 vs. 9.3 Mg DM ha^?1 year^?1 averaged for 1–11 years of growth). In the first year of the experiment, the energy inputs associated with the production of M. × giganteus and M. sacchariflorus were determined at 70.5 and 71.5 GJ/ha, respectively, and rhizomes accounted for around 78%–79% of total energy inputs. In the remaining years of cultivation, the total energy inputs associated with the production of both perennial rhizomatous grasses reached 13.6–15.7 (M. × giganteus) and 16.9–17.5 GJ ha^?1 year^?1 (M. sacchariflorus). Beginning from the second year of cultivation, mineral fertilizers were the predominant energy inputs in the production of M. × giganteus (78%–86%) and M. sacchariflorus (80%–82%). In years 2–11, the energy gain of M. × giganteus reached 50 (year 2) and 264–350 GJ ha^?1 year^?1 (years 3–11), and its energy efficiency ratio was determined at 4.7 (year 2) and 18.6–23.3 (years 3–11). The energy gain and the energy efficiency ratio of M. sacchariflorus biomass in the corresponding periods were determined at 87–234 GJ ha^?1 year^?1 and 6.1–14.3, respectively. Both grasses are significant and environmentally compatible sources of bioenergy, and they can be regarded as potential energy crops for Central‐Eastern Europe.     

Experimental study of wood downdraft gasification for an improved producer gas quality through an innovative two-stage air and premixed air/gas supply approach

This study conducted experiments on three different downdraft gasification approaches: single stage, conventional two-stage, and an innovative two-stage air and premixed air/gas supply approach. The innovative two-stage approach has two nozzle locations, one for air supply at combustion zone and the other located at the pyrolysis zone for supplying the premixed gas (air and producer gas). The producer gas is partially bypassed to mix with air and supplied to burn at the pyrolysis zone. The result shows that producer gas quality generated by the innovative two-stage approach improved as compared to conventional two-stage. The higher heating value (HHV) increased from 5.4 to 6.5 MJ/Nm³. Tar content in producer gas reduced to less than 45 mg/Nm³. With this approach, gas can be fed directly to an internal combustion engine. Furthermore, the gasification thermal efficiency also improved by approximately 14%. The approach gave double benefits on gas qualities and energy savings.     

Antiperoxidative and Antiinflammatory Effect of <Emphasis Type="Italic">Sida Cordifolia</Emphasis> Linn. on Quinolinic Acid Induced Neurotoxicity

Sida cordifolia is a plant belonging to the Malvaceae family used in many ayurvedic preparations. This study aimed at assessing the effects of ethanolic extract of Sida cordifolia root on quinolinic acid (QUIN) induced neurotoxicity and to compare its effect with the standard drug deprenyl in rat brain. Rats were divided into six groups: (1) control group (2) QUIN (55 μg/100 g bwt/day) (3) 50% ethanolic plant extract treated group (50 mg/100 g bwt/day) (4) Deprenyl (100 μg/100 g bwt/day) (5) QUIN (55 μg/100 g bwt/day) + 50% ethanolic plant extract treated group (50 mg/100 g bwt/day) (6) QUIN (55 μg/100 g bwt/day) + Deprenyl (100 μg/100 g bwt/day). At the end of the experimental period a status of lipid peroxidation products, protein peroxidation product, activities of the scavenging enzymes and the activities of the inflammatory markers were analyzed. Results revealed that the lipid peroxidation products decreased and the activities of the scavenging enzymes increased significantly in the brain of the plant extract treated group, deprenyl treated group and also in the coadminstered groups. The activities of markers of inflammatory responses such as cyclooxygenase and lipoxygenase were found to be significantly increased in the QUIN treated rats and this was decreased upon the administration of plant extract and deprenyl. In short, the study revealed that 50% ethanolic extract of Sida cordifolia has got potent antioxidant and antiinflammatory activity and the activity is comparable with the standard drug deprenyl.     

Energy Demands of Nitrogen Supply in Mass Cultivation of Two Commercially Important Microalgal Species, <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and <Emphasis Type="Italic">Dunaliella tertiolecta</Emphasis>

Mass culture of microalgae is a potential alternative to cultivation of terrestrial crops for bioenergy production. However, microalgae require nitrogen fertiliser in quantities much higher than plants, and this has important consequences for the energy balance of these systems. The effect of nitrogen fertiliser supplied to microalgal bubble-column photobioreactor cultures was investigated using different nitrogen sources (nitrate, urea, ammonium) and culture conditions (air, 12% CO₂). In 20 L cultivations, maximum biomass productivity for Chlorella vulgaris cultivated using nitrate and urea was 0.046 and 0.053 g L⁻¹ day⁻¹, respectively. Maximum biomass productivity for Dunaliella tertiolecta cultivated using nitrate, urea and ammonium was 0.033, 0.038 and 0.038 g L⁻¹ day⁻¹, respectively. In intensive bubble-column photobioreactors using 12% CO₂, maximum productivity reached 0.60 and 0.83 g L⁻¹ day⁻¹ for C. vulgaris and D. tertiolecta, respectively. Recycling of nitrogen within the photobioreactor system via algal exudation of nitrogenous compounds and bacterial activity was identified as a potentially important process. The energetic penalty incurred by supply of artificial nitrogen fertilisers, phosphorus, power and CO₂ to microalgal photobioreactors was investigated, although analysis of all energy burdens from biomass production to usable energy carriers was not conducted. After subtraction of the power, nitrogen and phosphorus energy burdens, maximum net energy ratios for C. vulgaris and D. tertiolecta cultivated in bubble columns were 1.82 and 2.10. Assuming CO₂ was also required from a manufactured source, the net energy ratio decreased to 0.09 and 0.11 for C. vulgaris and D. tertiolecta, so that biomass production in this scenario was unsustainable. Although supply of nitrogen is unlikely to be the most energetically costly factor in sparged photobioreactor designs, it is still a very significant penalty. There is a need to optimise both cultivation strategies and recycling of nitrogen in order to improve performance. Data are supported by measurements including biochemical properties (lipid, protein, heating value) and bacterial number by epifluorescence microscopy.     

Direct shoot regeneration from nodal explants of <Emphasis Type="Italic">Sida cordifolia</Emphasis> Linn

A method was developed to initiate multiple shoots from mature nodal explants of Sida cordifolia Linn. High frequency of regeneration was achieved on Murashige and Skoog (MS) medium supplemented with 2.0 mg l⁻¹ 6-benzylaminopurine, 0.5 mg l⁻¹ α-naphthalene acidic acid, 1.0 mg l⁻¹ adenine sulfate, and 10% (v/v) coconut milk. Multiple shoots were initiated within 21 d and the above media was capable of inducing the formation of more than 20 shoots from each explant. Regenerated shoots were successfully rooted on half-strength MS medium supplemented with 2.0 mg l⁻¹ indole-3-butyric acid and 3% (w/v) sucrose. Rooted plantlets were established in soil. The regenerated plantlets showed no morphological differences from the parent material. This protocol could be useful for germplasm conservation, cultivation, and genetic improvement of S. cordifolia.     

Comparative life cycle assessment of autotrophic cultivation of Scenedesmus dimorphus in raceway pond coupled to biodiesel and biogas production

Life cycle assessment (LCA) of indigenous freshwater microalgae, Scenedesmus dimorphus, cultivation in open raceway pond and its conversion to biodiesel and biogas were carried out. The LCA inventory inputs for the biogas scenario was entirely based on primary data obtained from algal cultivation (in pilot scale raceway pond), harvesting, and biogas production; while only the downstream processing involved in biodiesel production namely drying, reaction and purification were based on secondary data. Overall, eight scenarios were modeled for the integrated process involving: algae-based CO₂ capture and downstream processing scenarios for biodiesel and biogas along with impact assessment of nutrient addition and extent of recycling in a life cycle perspective. The LCA results indicated a huge energy deficit and net CO₂ negative in terms of CO₂ capture for both the biodiesel and biogas scenarios, majorly due to lower algal biomass productivity and higher energy requirements for culture mixing. The sensitivity analysis indicated that variability in the biomass productivity has predominant effect on the primary energy demand and global warming potential (GWP, kg CO₂ eq.) followed by specific energy consumption for mixing algal culture. Furthermore, the LCA results indicated that biogas conversion route from microalgae was more energy efficient and sustainable than the biodiesel route. The overall findings of the study suggested that microalgae-mediated CO₂ capture and conversion to biodiesel and biogas production can be energy efficient at higher biomass productivity (> 10 g m⁻² day⁻¹) and via employing energy-efficient systems for culture mixing (< 2 W m⁻³).

     

Process characteristics and products of olive kernel high temperature steam gasification (HTSG)

Exploitation of olive kernel for bioenergy production, with respect to the green house gases (GHGs) mitigation, is the main aim of this work. In this study, olive kernels were used as a solid biofuel, and high temperature steam gasification (HTSG) was investigated, in the fixed bed unit at KTH Sweden, with regard to hydrogen maximization in the produced gasification gas. Experiments were carried out in a temperature range of 750–1050 °C, with steam as the gasifying agent. The behaviour of olive kernels, under residence times from 120 up to 960 s, has been studied. At 1050 °C, a medium to high calorific value gas was obtained (LHV_gas = 13.62 MJ/Nm³), while an acquired H₂/CO molar ratio equal to four proved that olive kernel HTSG gasification could be an effective technology for a hydrogen-rich gas production (～40%vv H₂ in the produced gasification gas at 1050 °C). The produced char contained 79%ww of fixed carbon, low chlorine and sulphur content, which enables it for further re-use for energetic purposes. Tar content in the produced gas at 750 °C was 124.07 g/Nm³, while a 1050 °C at 79.64% reduction was observed and reached the value of 25.26 g/Nm³.     

Kinetics of CO conversion into H<Subscript>2</Subscript> by <Emphasis Type="Italic">Carboxydothermus hydrogenoformans</Emphasis>

The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H₂) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile suspended solid (VSS) L⁻¹. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g⁻¹ biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H₂ yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g⁻¹ VSS day⁻¹ were obtained at initial biomass densities between 5 and 8 mg VSS⁻¹. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g⁻¹ VSS day⁻¹ for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic carboxydotrophic species.     

Energy metabolism of Chironomus anthracinus (Diptera: Chironomidae) from the profundal zone of Lake Esrom,Denmark, as a function of body size,temperature and oxygen concentration

The profundal zone of Lake Esrom, Denmark has a dense population of Chironomus anthracinus, which survives 2–4 months of oxygen depletion each summer during stratification. The metabolism of 3rd and 4th instar larvae was examined in regard to variation in biomass and temperature. Respiration at air saturation was described by a curvilinear multiple regression relating oxygen consumption to individual AFDW and temperature. At 10 °C and varying oxygen regimes the O₂ consumption and CO₂ production of 4th instar larvae were almost unaltered from saturation to about 3 mg O₂ l^–1, but decreased steeply below this level. The respiratory quotient increased from 0.82 at saturation to about 3.4 at oxygen concentrations near 0.5 mg O₂ l^–1. This implied a shift from aerobic to partially anaerobic metabolism. At 0.5 mg O₂ l^–1 the total energy production equalled 20% of the rate at saturation of which more than one third was accounted for by anaerobic degradation of glycogen. This corresponded to a daily loss of 12 µg mg AFDW^–1 or approximately 5% of the body reserves. At unchanged metabolic rate the glycogen store would last three weeks, but long term oxygen deficiency causes a further suppression of the energy metabolism in C. anthracinus.     

Life cycle assessment of forest biomass energy feedstock in the Northeast United States

Life cycle assessment (LCA) was combined with primary data from nine forest harvesting operations in New York, Maine, Massachusetts, and Vermont, from 2013 to 2019 where forest biomass (FB) for bioenergy was one of several products. The objective was to conduct a data‐driven study of greenhouse gas emissions associated with FB feedstock harvesting operations in the Northeast United States. Deterministic and stochastic LCA models were built to simulate the current FB bioenergy feedstock supply chain in the Northeast US with a cradle‐to‐gate scope (forest harvest through roadside loading) and a functional unit of 1.0 Mg of green FB feedstock at a 50% moisture content. Baseline LCA, sensitivity analysis, and uncertainty analyses were conducted for three different FB feedstock types—dirty chips, clean chips, and grindings—enabling an empirically driven investigation of differences between feedstock types, individual harvesting process contributions, and literature comparisons. The baseline LCA average impacts were lower for grindings (4.57 kg CO_2eq/Mg) and dirty chips (7.16 kg CO_2eq/Mg) than for clean chips (23.99 kg CO_2eq/Mg) under economic allocation, but impacts were of similar magnitude under mass allocation, ranging from 24.42 to 27.89 kg CO_2eq/Mg. Uncertainty analysis showed a wider range of probable results under mass allocation compared to economic allocation. Sensitivity analysis revealed the impact of variations in the production masses and total economic values of primary products of forest harvests on the LCA results due to allocation of supply chain emissions. The high variability in fuel use between logging contractors also had a distinct influence on LCA results. The results of this study can aid decision‐makers in energy policy and guide emissions reductions efforts while informing future LCAs that expand the system boundary to regional FB energy pathways, including electricity generation, transportation fuels, pellets for heat, and combined heat and power.