Combustion Characteristics of Sewage Sludge and Algae

Sewage sludge is a good source of energetically desirable compounds and green algae in developing country like India. In this work, the combustion characteristics of sewage sludge and green algae are described. The calorific value (CV) of dried sewage sludge (n = 7) and green algae (n = 11) was ranged from 1800 to 6250 and 3700 to 6280 kcal/kg with mean value of 3999 ± 1347 and 4428 ± 547 kcal/kg, respectively. The effect of proximate variables and water quality parameters in the CV of sludge and algae are discussed.

Reproductive biology in an invasive plant Solidago canadensis

Solidago canadensis,a perennial Compositae plant originating from North America,was introduced into China as a horticultural plant in 1935.Under natural condi-tions,S.canadensis allocates large amounts of energy to sexual reproduction and produces many seeds,which reflects an r-strategy with high seed number and small seed size.In addition,naturalized populations have a great capacity to grow clonally with underground stems.S.canadensis has become an invasive weed in eastern China,and has caused serious damages to agricultural production and ecosystems in several provinces in China.In order to understand the reproductive characteristics of S.canadensis and effectively control its spread,we examined soil conditions,seed charac-teristics,seed germination and the capacity for asexual reproduction in different plant parts.We investigated the population dispersion of S.canadensis in fixed sites for three years,and analyzed the seasonal dynamics of the morphological parameters of the underground parts and the caloric values of different organs of S.canadensis.We also compared differences in the root systems of S.canadensis and composite exotic weeds.The following results were obtained:1)Under natural conditions,the germination season of S.canadensis lasts from March to October,with a peak from April to May.Vegetative growth and asexual reproduction are especially vigorous during summer due to high temperatures and soil drought stress.On the other hand,the rainy season proves suitable for seed germination.Most S.canadensis flower between September and January,and fruit in late October.A mature plant can produce about 20000 seeds.The mean weight of 1000 seeds ranges from 0.045 g to 0.050 g,and the mean seed moisture content ranges from 60%to 80%.The light-winged seeds disperse readily by air,water,vehicles,human activity or through livestock.2)S.canadensis seeds have a wide tolerance for different values of pH,salinity and soil moisture.The mean percent germination of seeds is 30%under suitable conditions.The results of seed germination under various environmental stresses and investigation of soil conditions indicate that well-aerated,slightly acidic soils with low salinity are suitable for the growth of S.canadensis.Additionally,S.canadensis has a high tolerance for contamination by heavy metal elements including Zn,Cu and Pb,but has low accumulation coefficients for these elements.3)S.canadensis reproduces asexually via underground rhizomes and nodes on the stem base to recruit new individuals,and in plants that experience mechanical damage,this repro-ductive strategy is used to produce clonal shoots.The capacity for asexual reproduction among different plant parts rank as follows:underground parts>stem-base(20 cm)>stem-base(30 cm)>stem-base(45 cm)>stem.Further,with increasing mechanical damage,the quantity of shoots produced by the plant decreases.4)The morphological parameters of the root system of S.canadensis including length,surface area,volume,and average diameter are greater than for composite exotic weeds.These parameters indicate that S.canadensis has the physiological potential to widely invade China.5)The aboveground growth rate and most of the underground morphological parameters vary remarkably among the seasons,with a peak normally occurring in September.In August,a fraction of the energy in leaves and stems is allocated underground to increase fine root growth and water uptake during hot weather.Additionally,the seasonal dynamics of the underground morphological parameters and the caloric values of different organs of S.canadensis enhance its reproductive ability.Based on the results above,we conclude that S.canadensis has great invasive potential in China.We suggest that urgent measures should be taken to control its further spread,and to minimize its impact on local plant diversity.

Effect of glycerol on densification of agricultural biomass

Experiments were conducted to verify the effect of adding glycerol for pelleting of selected agricultural crop residues,namely,wheat,barley,oat and canola straw.Single pelleting tests were conducted to study the effect of biomass type,hammer mill screen size,and crude glycerol content(co-product of biodiesel industry)on pellet quality(density and durability),ash content and gross heat of combustion.Four types of biomass were ground at three different hammer mill screen sizes of 6.4,3.2 and 1.6 mm.Each biomass was mixed with three levels of glycerol of 2.5%,5.0%and 7.5% by weight.Pellets were made at a pre-set load of 4400 N(138.9 MPa)using single-pelleting unit attached to an Instron testing machine.Quality of pellets was determined by measuring pellet density,relaxed density,durability(measured by pellet drop test)and specific energy required to make a pellet.The gross heat of combustion and ash content of pellets were also determined and compared.The highest pellet density(988-1133 kg/m^(3))and relaxed density(992-1142 kg/m^(3))were obtained from biomass ground using a hammer mill screen size of 6.4 mm.A decrease in hammer mill screen size resulted in reduced durability.The highest durability of biomass obtained from hammer mill screen size of 6.4 mm ranged from 97%-100%.Addition of glycerol resulted in lower ash content in majority of pellets.The highest gross heat of combustion was observed in pellets made from wheat straw with 7.5% glycerol content(38.3 MJ/kg).Addition of glycerol resulted in lower pellet densities,lower ash content,no change in durability and higher gross heating values.