Reduce Carbon Loss Research Articles

The Effects of Flue Gas Desulphurization Gypsum on the Properties of Dissolved Organic Matter and Bacterial Community During Composting

Composting is a process that converts organic materials including solid wastes into humus-like substances. Additives play an important role in regulating composting performances. This work investigated the influences of flue gas desulphurization gypsum (FGDG) on the properties and evolution of dissolved organic matter (DOM) during the co-composting of dairy manure, sugarcane leaf and pressmud (the sludge from sugar factory effluent) with the combination techniques of elemental analysis, particle size, zeta potential, UV–Vis spectroscopy and FT-IR technology. The results revealed that FGDG amendment reduced carbon loss and facilitated nitrogen emission in compost DOM, increased the aromaticity of DOM and compost maturity, enhanced the absorbance of –OH, –CHO, –COOH and C–O in polysaccharides. Additionally, the adding of FGDG was an inhibitive factor to the whole bacterial diversity during composting. These findings provided new insights into the evolution and properties of DOM and the microbial community during the composting process with FGDG amendment.

Simulation on photosynthetic light-responses of leaves of Quercus variabilis and Robinia pseudoacacia under different light conditions.

Photosynthesis can reflect the responses of plants to environmental changes. In this study, photosynthetic light-response curves were measured by the Li-6400XT photosynthetic system in Quercus variabilis and Robinia pseudoacacia plantations in Xiaolangdi Forest Ecosystem Research Station. Photosynthetic light-response curves were fitted by Ye model. The differences of photosynthetic parameters between inner and margin forests were examined. Stomatal conductance (gs) light-response curve were fitted using the mechanism model of gs coupled with a modified model of light-response of photosynthesis. The light-response characteristics of gs were investigated. Net photosynthetic rates (Pn) of Q. variabilis in the inner forest was higher than that in the margin. The initial light efficiency (Α) was 12.4% more in the inner forest than that in the margin in July and August when photosynthetically active radiation was less than 200 Μmol·m-2·s-1. The ability to capture and utilize weak light of Q. variabilis leaves in the inner forest was obviously higher than that in the margin. When photosynthetically active radiation was higher than 200 Μmol·m-2·s-1, Pn of Q. variabilis leaves in the margin forest was larger than that in the inner. Under weak light conditions (0-200 Μmol·m-2·s-1), Pn of R. pseudoacacia in the inner forest was higher than that in the margin. Pn of R. pseudoacacia in the inner forest was less than that in the margin when light intensity was higher than 200 Μmol·m-2·s-1. The dark respiration rate (Rd) and light compensation point (Ic) in the inner forest were 50.0% and 42.8% lower than those in the margin. The less Rd and Ic of the inner forest could reduce carbon loss and adapt to low photosynthetic rate. The stomatal conductance light-response of R. pseudoacacia in the inner forest significantly differed from that in the margin. The leaves of Q. variabilis and R. pseudoacacia had strong adaptability to the changes of light condition. The values of maximum net photosynthetic rate (Pn max) and Α of Q. variabilis leaves were mainly controlled by gs, and Rd and Ic were primarily affected by air temperature. Pn max and Α of R. pseudoacacia leaves had significant positive correlation with air temperature. The Ic and the light saturation point (Is) were remarkably correlated with leaf saturation vapor pressure deficit.

PERFORMANCE OF A TANGENTIALLY FIRED BOILER IN A THERMAL POWER PLANT

The most effective method for producing intense turbulence is by the impingement of one flame on another. This action is secured through the use of burners located in each of the four corners of the furnace. The burner nozzles are so directed that the streams of coal and air are projected along a line tangent to a small circle, lying in a horizontal plane, at the centre of the furnace. A scrubbing action is present which assures contact between the combustible and oxygen, thus promoting rapid combustion and reducing carbon loss. The experimental results of this study can be summarized as the use of tangentially fired boiler which increase splendid air-fuel mixture and pulverized coal is entrained in Primary Air (PA), and in-addition to that the Secondary Air (SA) is also projected towards the mill, finally a rotating “FIRE BALL” is formed. The present work analysis is carried out on Tangentially Fired Boiler by considering heat input through four burners. The heat output is determined by considering various losses from the boiler that is loss due to dry gas, loss due to moisture, loss due to H2 for combustion, heat loss due to combustile and refuse and losses due to radiation etc. In addition heat absorbed by economizer, boilers, superheater and reheater are studied, thus finally the net heat absorbed and thermal efficiency of tangentially fired boiler are determined. Graphs are drawn to evaluate the various effects of heat input on output parameters in the boiler. Sankey diagrams are drawn to show the performance in the boiler. The values calculated are put and shown as tables in Appendix.

English

The yield of soybean was influenced by the chemical and microbiological properties of the soil, which was favored by management techniques that promote improvement in soil quality. The objective of this study was to evaluate soybean yield, chemical and microbiological quality of the soil as a function of biological fertilization and soil cover conditions. The experiment was conducted in both crops seasons 2015/16 and 2016/17 with experimental design in randomized blocks, with the agronomic characteristics of the soybean analyzed as a function of the factors of biological fertilization and soil cover conditions, as well as the chemical and microbiological indicators of the soil, besides the two factors mentioned earlier, fragment of forest. It was observed higher height of plants, pods with three grains, leaf area and yield of soybean cultivated on Crotalaria ochroleuca, followed by Pennisetum glaucum. Biological fertilizer, P. glaucum and C. ochroleuca promoted increases in the fertility of soil cultivated with soybean, mainly potassium, and contributed to reduce carbon losses, indicated by lower basal respiration and soil metabolic quotient. Based on the results, we conclude that the soybean presented highest grain yield with C. ochroleuca, and the biological fertilization and cover plants increased the chemical and microbiological quality of the soil. These techniques can be implemented in the soybean farming system. Key words: Fertility of soil, microbiological quality, Glycine max, yield, management.

Identification of Carbon loss in the production of pilot-scale Carbon nanotube using gauze reactor

Carbon loss more than 65% was the major obstacles in the Carbon Nanotube (CNT) production using gauze pilot scale reactor. The results showed that the initial carbon loss calculation is 27.64%. The calculation of carbon loss, then, takes place with various corrections parameters of: product flow rate error measurement, feed flow rate changes, gas product composition by Gas Chromatography Flame Ionization Detector (GC FID), and the carbon particulate by glass fiber filters. Error of product flow rate due to the measurement with bubble soap gives calculation error of carbon loss for about ± 4.14%. Changes in the feed flow rate due to CNT growth in the reactor reduce carbon loss by 4.97%. The detection of secondary hydrocarbon with GC FID during CNT production process reduces carbon loss by 5.14%. Particulates carried by product stream are very few and merely correct the carbon loss about 0.05%. Taking all the factors into account, the amount of carbon loss within this study is (17.21 ± 4.14)%. Assuming that 4.14% of carbon loss is due to the error measurement of product flow rate, the amount of carbon loss is 13.07%. It means that more than 57% of carbon loss within this study is identified.

Evidence for the role and fate of water-insoluble condensed tannins in the short-term reduction of carbon loss during litter decay

Warmer temperatures associated with climate change have the potential to accelerate litter decay and subsequently release large amounts of carbon stored in soils. Condensed tannins are widespread secondary metabolites, which accumulate to high concentrations in many woody plants and play key roles in forest soil nutrient cycles. Future elevated atmospheric CO2 concentrations are predicted to reduce nitrogen content and increase tannin concentrations in plant tissues, thus reducing litter quality for microbial communities and slowing decomposition rates. How the distinct condensed tannin fractions (water-soluble, acetone:MeOH-soluble and solvent-insoluble) impact soil processes, has not been investigated. We tested the impact of condensed tannin and nitrogen concentrations on decay rates of poplar and Douglas-fir litter at sites spanning temperature and moisture gradients in coastal rainshadow forests in British Columbia, Canada. The three condensed tannin fractions were quantified using recent improvements on the butanol-HCl assay. Decay was assessed based on carbon remaining, while changes in litter chemistry were primarily observed using two methods for proximate chemical analyses. After 0.6 and 1 year of decay, more carbon remained in poplar litter with high, compared to low, condensed tannin concentrations. By contrast, more carbon remained in Douglas fir litter than poplar litter during this period, despite lower condensed tannin concentrations. Rapid early decay was especially attributed to loss of soluble compounds, including water-soluble condensed tannins. Water-insoluble condensed tannin fractions, which were transformed to acid-unhydrolyzable residues over time, were associated with reduced carbon loss in high condensed tannin litter.

Influence of poly (dihydroxybiphenyl borate) on the curing behaviour and thermal pyrolysis mechanism of phenolic resin

In this study, phenolic resin (PR) that is modified with poly (dihydroxybiphenyl borate) (PDDB) is prepared. The chemical structure, thermal properties and structural evolution at high temperatures for cured PDDB/PR are investigated to understand the reason for high char yields. The results show that the phenylborates that are formed during curing are attributed to the high char yield of PDDB/PR (74%, 800 °C). Phenylborates can block parts of phenolic hydroxyl and effectively inhibit their thermal decomposition reaction. By tracking the resin residue and volatiles that are released during pyrolysis, it is determined that boron oxide and boron carbide are formed via pyrolysis and help reduce carbon loss. Introducing PDDB into PR improves the graphitization degree and graphite crystallites of carbonization products, which promotes the formation of ordered glassy carbon during pyrolysis. Additionally, the CF/PDDB/PR composites show excellent mechanical and ablation properties due to good interfacial adhesion between resin matrix and fibre. This method makes it possible for using PDDB to enhance the thermal properties of the polymer with lower cost, more functions and broader applications.

PLANT SHOOTS AND ROOTS BIOMASS OF BRACHIARIA GRASSES AND THEIR EFFECTS ON SOIL CARBON IN THE SEMI-ARID TROPICS OF KENYA

<p>Grassland management practices that improve carbon uptake by increasing productivity or reducing carbon losses can lead to net accumulation of carbon in soils. A study was conducted to quantify the amounts of shoots and roots biomass of Brachiaria grass cultivars and their effects on soil carbon in two sites, Ithookwe and Katumani in semi-arid tropical Kenya. The grass cultivars were<em> Brachiaria decumbens </em>cv. Basilisk, <em>B. brizantha</em> cvs. Marandu, MG4, Piatã and Xaraes, <em>B. humidicola</em> cv. Llanero and <em>B. hybrid</em> cv. Mulato II. These were compared with two locally cultivated grasses (<em>Chloris gayana</em> cv<em>. </em>KAT R3 and <em>Pennisetum purpureum </em>cv<em>. </em>Kakamega 1). The grass treatments were evaluated with fertilizer application (40 kg P applied at sowing and 50 kg N ha<sup>-1</sup> in each wet season) and with no fertilizer application. Shoots biomass of the Brachiaria cultivars ranged from 3.0 to 11.3 t ha<sup>-1</sup> and 5.5 to 8.3 t ha<sup>-1</sup> at Ithookwe and Katumani sites respectively in year 1. The highest shoots biomass recorded at Ithookwe was from cv. Piata while cv. MG4 gave the highest biomass at Katumani. Similar trends were recorded in year 2 of growth though the shoots biomass was lower at Katumani. However, the yields were significantly lower than those recorded from control, Napier grass in both years. The cv. Marandu, Xaraes, Basilisk and Piata had higher roots biomass than the controls (Rhodes grass and Napier grass) indicating greater potential for the Brachiaria grasses to sequester more carbon in the soil. The results of this study indicate that introduction of Brachiaria grasses in the semi-arid tropics of Kenya and in other similar environments can help increase soil carbon stocks that would mitigate the adverse effects of climate change and have greater economic returns. </p>

Growth of Carbon Nanofibers in Phenolic Resin for Carbon-Contained Refractory Using Different Catalysts

Various phenolic resins modified with carbon nanofibers were prepared using Fe(NO3)3, Co(NO3)2, and Ni(NO3)3 as catalyst, respectively. The influences of different catalysts on the phase, microstructure evolution, and oxidation resistance of the modified phenolic resin were investigated by X-ray diffraction analysis, field-emission scanning electron microscopy, and thermal gravimetric analysis. The results showed that, compared with a single catalyst, the mixed catalysts (Co(NO3)2 : Fe(NO3)3 = 1 : 1) promoted the growth of the carbon nanofibers, which have the higher crystallinity, homogeneous dispersion, and nonagglomeration. These carbon nanofibers can effectively reduce carbon losses, increase char yield, and fill the holes in the thermal cracking process of phenolic resins.

Functional expression and evaluation of heterologous phosphoketolases in Saccharomyces cerevisiae.

Phosphoketolases catalyze an energy- and redox-independent cleavage of certain sugar phosphates. Hereby, the two-carbon (C2) compound acetyl-phosphate is formed, which enzymatically can be converted into acetyl-CoA—a key precursor in central carbon metabolism. Saccharomyces cerevisiae does not demonstrate efficient phosphoketolase activity naturally. In this study, we aimed to compare and identify efficient heterologous phosphoketolase enzyme candidates that in yeast have the potential to reduce carbon loss compared to the native acetyl-CoA producing pathway by redirecting carbon flux directly from C5 and C6 sugars towards C2-synthesis. Nine phosphoketolase candidates were expressed in S. cerevisiae of which seven produced significant amounts of acetyl-phosphate after provision of sugar phosphate substrates in vitro. The candidates showed differing substrate specificities, and some demonstrated activity levels significantly exceeding those of candidates previously expressed in yeast. The conducted studies also revealed that S. cerevisiae contains endogenous enzymes capable of breaking down acetyl-phosphate, likely into acetate, and that removal of the phosphatases Gpp1 and Gpp2 could largely prevent this breakdown. An evaluation of in vivo function of a subset of phosphoketolases was conducted by monitoring acetate levels during growth, confirming that candidates showing high activity in vitro indeed showed increased acetate accumulation, but expression also decreased cellular fitness. The study shows that expression of several bacterial phosphoketolase candidates in S. cerevisiae can efficiently divert intracellular carbon flux toward C2-synthesis, thus showing potential to be used in metabolic engineering strategies aimed to increase yields of acetyl-CoA derived compounds.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0290-0) contains supplementary material, which is available to authorized users.

Global Food Demand and Carbon-Preserving Cropland Expansion under Varying Levels of Intensification

Increasing demand for agricultural crops and a decline in the rate of yield improvements will require expansion of cropland (extensification), resulting in a loss of carbon storage. This paper uses global, spatially explicit data to analyze how extensification can be located to meet crop demand in a way that minimizes carbon losses under varying levels of intensification. Carbon-preserving extensification can reduce carbon loss by 7.3 billion tons compared to proportionally increasing extensification by 2050, valued at $1.3 trillion (2012 dollars) based on an estimated social cost of carbon of $181 per ton of carbon (∼$50 per ton CO 2 ).

Structure and thermal pyrolysis mechanism of poly(resorcinol borate) with high char yield

Boron-containing organic polymers have excellent thermal stability and flame retardancy. Hyperbranched polymers, in which boron atoms are introduced in the form of borates, exhibit superior performance and have more applicability. This work focuses on the boron-containing polymer poly (resorcinol borate) (PRB). The chemical structure of PRB and its structural evolution at high temperatures are investigated in order to clarify the reason for its high char yield. The results indicate that the molecular skeleton of PRB mainly consists of aromatic structures, borates, BOB structures, and a small number of boron hydroxyl groups and phenolic hydroxyl groups. During pyrolysis, boron oxide is formed by the cleavage of borate OC bonds at about 400 °C. This process effectively avoids the formation and release of volatile carbon dioxide, reducing carbon loss. A large fraction of the carbon from aromatic rings is converted to amorphous carbon via pyrolysis, which possesses higher thermal stability. These results can guide the design and synthesis of novel boron-containing polymers and can provide a strategy for modifying the thermal properties of phenolic resins in order to broaden their applicability in the field of ablative-resistant composites and coatings.

EFFECTS OF ORGANIC AND CHEMICAL FERTILIZER INPUTS ON BIOMASS PRODUCTION AND CARBON DYNAMICS IN A MAIZE FARMING ON ULTISOLS

An effort to increase the yield and reduce carbon loss from maize farming practices on Ultisols largely depend on fertilizer inputs and in situ crop residual management. The experiment aimed to estimate yields, biomass production and carbon dynamics of several management fertilization on maize farming practice on Ultisols has been conducted from March to July 2013 in Taman-bogo Experimental Farm, East Lampung. The experiment was set up as a randomized complete blockdesign, consisted of 6 treatments namely: 5 t ha -1 of cattle manure, 5 t ha - 1 of dried sludge manure, and its combination with 200 kg urea ha -1 + 125 kg SP36 ha -1 + 50 kg KCl ha -1 (50% of recommended dose of inorganic fertilizers “RDIF”) and 75% of RDIF. The experimental results revealed that application of combined organic with inorganic fertilizers increased the biomass production, carbon fixation, and grain yield significantly. More than 50% of produced biomass and fixed carbon (grain, maize cob, maize husk, stems and leaves) were removed from maize farming. The use of organic fertilizer combined with NPK fertilizer at 50% of RDIF can be applied to increase the biomass production, organic carbon fixation and maize grain yield in sustainable ways.

The Effect of Simulated Nitrogen Deposition on the Emission of Carbonyl Compounds from Ormosia pinnata and Cinnamomum burmannii

The Effect of Simulated Nitrogen Deposition on the Emission of Carbonyl Compounds from Ormosia pinnata and Cinnamomum burmannii Elevated anthropogenic nitrogen (N) deposition has become a limiting factor for plants instead of a nutrient for its dramatic rising at globally scale, which greatly affects the process of carbon (C) cycle from individual plant to ecosystem, and even global levels. It could affect biogenic carbonyl emissions as an important component of carbon pool from plants, but this aspect has not yet been investigated. In this study, we performed a simulated N deposition experiment (100 kg N•ha-1•y-1) on two native tree saplings planted in a nursery in South China. Results showed that three main biogenic carbonyls, i.e. formaldehyde, acetaldehyde, and acetone from tree leaves all had distinct seasonal variations, with much higher emission rates in the wet season than in the dry season. Elevated N addition significantly depressed the emission of biogenic carbonyls in the dry season, but not in the wet season. No big differences were observed in carbonyls emissions from the two tree species responding to N deposition both in the wet season and in the dry season. Thus, we concluded that N deposition might drive plants to change carbon allocation and reduce carbon loss when as a limiting factor in the dry season. This finding is of significance for the theory of carbon allocation and plant adaptability strategy under elevated N deposition.

Climate Clever Beef: options to improve business performance and reduce greenhouse gas emissions in northern Australia

The Rangeland Journal – Climate Clever Beef special issue examines options for the beef industry in northern Australia to contribute to the reduction in global greenhouse gas (GHG) emissions and to engage in the carbon economy. Relative to its gross value (A$5 billion), the northern beef industry is responsible for a sizable proportion of national reportable GHG emissions (8–10%) through enteric methane, savanna burning, vegetation clearing and land degradation. The industry occupies large areas of land and has the potential to impact the carbon cycle by sequestering carbon or reducing carbon loss. Furthermore, much of the industry is currently not achieving its productivity potential, which suggests that there are opportunities to improve the emissions intensity of beef production. Improving the industry’s GHG emissions performance is important for its environmental reputation and may benefit individual businesses through improved production efficiency and revenue from the carbon economy. The Climate Clever Beef initiative collaborated with beef businesses in six regions across northern Australia to better understand the links between GHG emissions and carbon stocks, land condition, herd productivity and profitability. The current performance of businesses was measured and alternate management options were identified and evaluated. Opportunities to participate in the carbon economy through the Australian Government’s Emissions Reduction Fund (ERF) were also assessed. The initiative achieved significant producer engagement and collaboration resulting in practice change by 78 people from 35 businesses, managing more than 1 272 000 ha and 132 000 cattle. Carbon farming opportunities were identified that could improve both business performance and emissions intensity. However, these opportunities were not without significant risks, trade-offs and limitations particularly in relation to business scale, and uncertainty in carbon price and the response of soil and vegetation carbon sequestration to management. This paper discusses opportunities for reducing emissions, improving emission intensity and carbon sequestration, and outlines the approach taken to achieve beef business engagement and practice change. The paper concludes with some considerations for policy makers.

Changes in soil organic carbon in the upper Heihe river basin, China

The Heihe River Basin is a globally significant carbonpool, but its soil organic carbon dynamics is poorly understood. Soilsamples taken between 2500 m and 4100 m revealed that the majority(>75%) of soil organic carbon was from 0-40 cm. It showed anegative relationship with pH and soil bulk density, and a positiverelationship with altitude and soil water content, respectively. From2005 to 2011, soil carbon content in the upper catchment decreasedfrom 93 g/kg to 53 g/kg. These results suggest that policies shouldaim to reduce carbon loss by transferring it from the top- to thesub-soil.

A photorespiratory bypass increases plant growth and seed yield in biofuel crop Camelina sativa.

BackgroundCamelina sativa is an oilseed crop with great potential for biofuel production on marginal land. The seed oil from camelina has been converted to jet fuel and improved fuel efficiency in commercial and military test flights. Hydrogenation-derived renewable diesel from camelina is environmentally superior to that from canola due to lower agricultural inputs, and the seed meal is FDA approved for animal consumption. However, relatively low yield makes its farming less profitable. Our study is aimed at increasing camelina seed yield by reducing carbon loss from photorespiration via a photorespiratory bypass. Genes encoding three enzymes of the Escherichia coli glycolate catabolic pathway were introduced: glycolate dehydrogenase (GDH), glyoxylate carboxyligase (GCL) and tartronic semialdehyde reductase (TSR). These enzymes compete for the photorespiratory substrate, glycolate, convert it to glycerate within the chloroplasts, and reduce photorespiration. As a by-product of the reaction, CO2 is released in the chloroplast, which increases photosynthesis. Camelina plants were transformed with either partial bypass (GDH), or full bypass (GDH, GCL and TSR) genes. Transgenic plants were evaluated for physiological and metabolic traits.ResultsExpressing the photorespiratory bypass genes in camelina reduced photorespiration and increased photosynthesis in both partial and full bypass expressing lines. Expression of partial bypass increased seed yield by 50–57 %, while expression of full bypass increased seed yield by 57–73 %, with no loss in seed quality. The transgenic plants also showed increased vegetative biomass and faster development; they flowered, set seed and reached seed maturity about 1 week earlier than WT. At the transcriptional level, transgenic plants showed differential expression in categories such as respiration, amino acid biosynthesis and fatty acid metabolism. The increased growth of the bypass transgenics compared to WT was only observed in ambient or low CO2 conditions, but not in elevated CO2 conditions.ConclusionsThe photorespiratory bypass is an effective approach to increase photosynthetic productivity in camelina. By reducing photorespiratory losses and increasing photosynthetic CO2 fixation rates, transgenic plants show dramatic increases in seed yield. Because photorespiration causes losses in productivity of most C3 plants, the bypass approach may have significant impact on increasing agricultural productivity for C3 crops.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0357-1) contains supplementary material, which is available to authorized users.

Phosphorus-assisted biomass thermal conversion: reducing carbon loss and improving biochar stability.

There is often over 50% carbon loss during the thermal conversion of biomass into biochar, leading to it controversy for the biochar formation as a carbon sequestration strategy. Sometimes the biochar also seems not to be stable enough due to physical, chemical, and biological reactions in soils. In this study, three phosphorus-bearing materials, H3PO4, phosphate rock tailing (PRT), and triple superphosphate (TSP), were used as additives to wheat straw with a ratio of 1: 0.4–0.8 for biochar production at 500°C, aiming to alleviate carbon loss during pyrolysis and to increase biochar-C stabilization. All these additives remarkably increased the biochar yield from 31.7% (unmodified biochar) to 46.9%–56.9% (modified biochars). Carbon loss during pyrolysis was reduced from 51.7% to 35.5%–47.7%. Thermogravimetric analysis curves showed that the additives had no effect on thermal stability of biochar but did enhance its oxidative stability. Microbial mineralization was obviously reduced in the modified biochar, especially in the TSP-BC, in which the total CO2 emission during 60-d incubation was reduced by 67.8%, compared to the unmodified biochar. Enhancement of carbon retention and biochar stability was probably due to the formation of meta-phosphate or C-O-PO3, which could either form a physical layer to hinder the contact of C with O2 and bacteria, or occupy the active sites of the C band. Our results indicate that pre-treating biomass with phosphors-bearing materials is effective for reducing carbon loss during pyrolysis and for increasing biochar stabilization, which provides a novel method by which biochar can be designed to improve the carbon sequestration capacity.

Enhanced Australian carbon sink despite increased wildfire during the 21st century

Climate projections show Australia becoming significantly warmer during the 21st century, and precipitation decreasing over much of the continent. Such changes are conventionally considered to increase wildfire risk. Nevertheless, we show that burnt area increases in southern Australia, but decreases in northern Australia. Overall the projected increase in fire is small (0.72–1.31% of land area, depending on the climate scenario used), and does not cause a decrease in carbon storage. In fact, carbon storage increases by 3.7–5.6 Pg C (depending on the climate scenario used). Using a process-based model of vegetation dynamics, vegetation–fire interactions and carbon cycling, we show increased fire promotes a shift to more fire-adapted trees in wooded areas and their encroachment into grasslands, with an overall increase in forested area of 3.9–11.9%. Both changes increase carbon uptake and storage. The increase in woody vegetation increases the amount of coarse litter, which decays more slowly than fine litter hence leading to a relative reduction in overall heterotrophic respiration, further reducing carbon losses. Direct CO2 effects increase woody cover, water-use efficiency and productivity, such that carbon storage is increased by 8.5–14.8 Pg C compared to simulations in which CO2 is held constant at modern values. CO2 effects tend to increase burnt area, fire fluxes and therefore carbon losses in arid areas, but increase vegetation density and reduce burnt area in wooded areas.

Effects of mineral additives on biochar formation: carbon retention, stability, and properties.

Biochar is being recognized as a promising tool for long-term carbon sequestration, and biochar with high carbon retention and strong stability is supposed to be explored for that purpose. In this study, three minerals, including kaolin, calcite (CaCO3), and calcium dihydrogen phosphate [Ca(H2PO4)2], were added to rice straw feedstock at the ratio of 20% (w/w) for biochar formation through pyrolysis treatment, aiming to improve carbon retention and stabilization in biochar. Kaolin and CaCO3 had little effect on the carbon retention, whereas Ca(H2PO4)2 increased the carbon retention by up to 29% compared to untreated biochar. Although the carbon loss from the kaolin-modified biochar with hydrogen peroxide oxidation was enhanced, CaCO3 and Ca(H2PO4)2 modification reduced the carbon loss by 18.6 and 58.5%, respectively. Moreover, all three minerals reduced carbon loss of biochar with potassium dichromate oxidation from 0.3 to 38.8%. The microbial mineralization as CO2 emission in all three modified biochars was reduced by 22.2-88.7% under aerobic incubation and 5-61% under anaerobic incubation. Enhanced carbon retention and stability of biochar with mineral treatment might be caused by the enhanced formation of aromatic C, which was evidenced by cross-polarization magic angle spinning (13)C nuclear magnetic resonance spectra and Fourier transform infrared spectroscopy analysis. Our results indicated that the three minerals, especially Ca(H2PO4)2, were effective in increasing carbon retention and strengthening biochar stabilization, which provided a novel idea that people could explore and produce the designated biochar with high carbon sequestration capacity and stability.