Algal Biochar Research Articles

Good for sewage treatment and good for agriculture: Algal based compost and biochar

In this study we test a novel approach to closing the anthropogenic nutrient cycle, by using the freshwater macroalga, Oedogonium intermedium, to recover dissolved nitrogen (N) and phosphorous (P) from municipal wastewater. We then convert this cultivated algae into two types of soil ameliorant; compost and biochar. To produce compost, algae was combined with sugarcane bagasse and left to mature for 10 weeks, and to produce biochar, algae was processed through slow pyrolysis at 450 °C. The mature compost had a total N and P content of 2.5% and 0.6%, which was 2- to 4-times lower than the algal biochar, which had a total N and P content of 5.5% and 2.5% respectively. Composting stabilized the N and P recovered from wastewater, with 80% of the initial N and >99% of the initial P retained in the mature compost. In contrast, only 29% of the initial N and 62% of the initial P was retained in the biochar. When the mature compost was added to a low fertility soil it significantly increased the production of sweet corn (Zea mays). Treatments receiving 50 and 100% compost produced 4–9 times more corn biomass than when synthetic fertilizer alone was added to the low fertility soil. When biochar was applied in conjunction with compost there was an additional 15% increase in corn productivity, most likely due to the ability of the biochar to bind labile N and P and prevent its loss from the soil. This study demonstrates a unique model for recovering N and P from municipal wastewater and recycling these nutrients into the agricultural industry. This could be an ideal model for regional areas where agriculture and water treatment facilities are co-located and could ultimately reduce the reliance of agriculture on finite mineral sources of P.

Biosorption of Co (II) from aqueous solution using algal biochar: Kinetics and isotherm studies

The present investigation deals with the utilization of biochar derived from the pyrolysis of microalgae Scenedesmus dimorphus as an adsorbent for the removal of cobalt (II) ion (Co) from aqueous solution. A series of experiments were conducted in a batch system to evaluate the performance of the biochar for Co removal. The effect of contact time on adsorption of Co (II) onto surface of the biochar was investigated. The equilibrium sorption data were analyzed by using Langmuir, Freundlich, Temkin, Harkins-Jura and Dubinin-Radushkevich (D-R) isotherms and were found to be adequate in describing the Co adsorption onto the biochar. Equilibrium data were well fitted for Freundlich, Temkin and D-R isotherms. The kinetic study of Co (II) adsorption on microalgae biochar were described by applying pseudo-first-order and pseudo-second-order rate equations. The surface of adsorbent before and after the removal of Co (II) was characterized by using SEM, EDX and XRD analysis.

Algal biochar enhances the re-vegetation of stockpiled mine soils with native grass

In most countries the mining industry is required to rehabilitate disturbed land with native vegetation. A typical approach is to stockpile soils during mining and then use this soil to recreate landforms after mining. Soil that has been stockpiled for an extended period typically contains little or no organic matter and nutrient, making soil rehabilitation a slow and difficult process. Here, we take freshwater macroalgae (Oedogonium) cultivated in waste water at a coal-fired power station and use it as a feedstock for the production of biochar, then use this biochar to enhance the rehabilitation of two types of stockpiled soil – a ferrosol and a sodosol – from the adjacent coal mine. While the biomass had relatively high concentrations of some metals, due to its cultivation in waste water, the resulting biochar did not leach metals into the pore water of soil-biochar mixtures. The biochar did, however, contribute essential trace elements (particularly K) to soil pore water. The biochar had very strong positive effects on the establishment and growth of a native plant (Kangaroo grass, Themeda australis) in both of the soils. The addition of the algal biochar to both soils at 10 t ha−1 reduced the time to germination by the grass and increased the growth and production of plant biomass. Somewhat surprisingly, there was no beneficial effect of a higher application rate (25 t ha−1) of the biochar in the ferrosol, which highlights the importance of matching biochar application rates to the requirements of different types of soil. Nevertheless, we demonstrate that algal biochar can be produced from biomass cultivated in waste water and used at low application rates to improve the rehabilitation of a variety of soils typical of coal mines. This novel process links biomass production in waste water to end use of the biomass in land rehabilitation, simultaneously addressing two environmental issues associated with coal-mining and processing.

Bioremediation for coal-fired power stations using macroalgae

Macroalgae are a productive resource that can be cultured in metal-contaminated waste water for bioremediation but there have been no demonstrations of this biotechnology integrated with industry. Coal-fired power production is a water-limited industry that requires novel approaches to waste water treatment and recycling. In this study, a freshwater macroalga (genus Oedogonium) was cultivated in contaminated ash water amended with flue gas (containing 20% CO2) at an Australian coal-fired power station. The continuous process of macroalgal growth and intracellular metal sequestration reduced the concentrations of all metals in the treated ash water. Predictive modelling shows that the power station could feasibly achieve zero discharge of most regulated metals (Al, As, Cd, Cr, Cu, Ni, and Zn) in waste water by using the ash water dam for bioremediation with algal cultivation ponds rather than storage of ash water. Slow pyrolysis of the cultivated algae immobilised the accumulated metals in a recalcitrant C-rich biochar. While the algal biochar had higher total metal concentrations than the algae feedstock, the biochar had very low concentrations of leachable metals and therefore has potential for use as an ameliorant for low-fertility soils. This study demonstrates a bioremediation technology at a large scale for a water-limited industry that could be implemented at new or existing power stations, or during the decommissioning of older power stations.

Algal biochar: effects and applications

AbstractAlgae represent a promising target for the generation of bioenergy through slow pyrolysis, leading to the production of biochar. This study reports experiments conducted on the production of freshwater and saltwater macroalgal biochar in pilot‐scale quantities, the physical and chemical characteristics of the biochars, and their impact on plant growth. The biochars are low in carbon (C) content, surface area and cation exchange capacity, while being high in ash and nutrients. Trace element analysis demonstrates that macroalgal biochar produced from unpolluted water does not contain toxic trace elements in excess of levels mandated for unrestricted use as a biosolids amendment to soils. Pot trials conducted using a C and nutrient‐poor soil, without and with additional fertilizer, demonstrate dramatic increases between 15 and 32 times, respectively, in plant growth rate for biochar treatments compared with the no biochar controls, with additional smaller increases when fertilizer was added. Pot trials conducted using a relatively fertile agricultural soil showed smaller but significant impacts of biochar amendment over the controls.

Algal biochar – production and properties

This study presents baseline data on the physiochemical properties and potential uses of macroalgal (seaweed) biochar produced by pyrolysis of eight species of green tide algae sourced from fresh, brackish and marine environments. All of the biochars produced are comparatively low in carbon content, surface area and cation exchange capacity, but high in pH, ash, nitrogen and extractable inorganic nutrients including P, K, Ca and Mg. The biochars are more similar in characteristics to those produced from poultry litter relative to those derived from ligno-cellulosic feedstocks. This means that, like poultry litter biochar, macroalgal biochar has properties that provide direct nutrient benefits to soils and thereby to crop productivity, and will be particularly useful for application on acidic soils. However, macroalgal biochars are volumetrically less able to provide the carbon sequestration benefits of the high carbon ligno-cellulosic biochars.