Byron Eco Park Biochar Seminars
WHAT IS BIOCHAR?
Biochars refer to the carbon-rich materials (charcoal) produced from the slow pyrolysis (heating in the absence of oxygen) of biomass. Recently, there has been much interest in biochars as soil amendments to improve and maintain soil fertility and to increase soil carbon sequestration. The capacity to sequester carbon in the soil can be attributed to the relative stable nature and, therefore, long turnover time of biochar in soil and is of particular relevance to the solution of climate change. While it is difficult to estimate how long newly created biochar will stay in the soil some suggest it could be for as long as five thousand years.
Biochar may be an immediate solution to reducing the global impact of farming (and in reducing the impact from all agricultural waste). The burning and natural decomposition of trees and agricultural matter contributes a large amount of CO2 released to the atmosphere. Biochar can store this carbon in the ground, potentially making a significant reduction in atmospheric Greenhouse gas (GHG) levels; at the same time its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity and reduce pressure on old growth forests.
In specific locations - e.g. at the tropical forest frontier in Central Africa amongst ultra-poor communities of slash-and-burn farmers - biochar may become the kernel of a highly integrated sustainable development and poverty alleviation concept that can tackle key issues simultaneously: hunger and food insecurity, low agricultural productivity and soil depletion, deforestation and biodiversity loss, energy poverty (and related health problems such as indoor air pollution), and climate change. In this concept, multiple mitigation benefits would come from the char in the soil (carbon sink), the avoided deforestation and its associated emissions, and the emissions avoided by making a switch from cooking with unsustainably harvested fuel wood on inefficient open fires to more efficient biochar-generating, small-scale energy production.
As a result of significant product variations due to varying technology, process conditions, and feedstock compositions, biochar cannot be considered a commodity product. Biochar is sold under a range of brand names.
Current biochar projects are small scale, though recent technological developments show that organic matter can be efficiently turned into biochar using advanced pyrolysis processes, potentially making a significant impact on the overall global carbon budget.
How is ‘biochar’ made?
Biochar is made by heating biomass under oxygen-limited conditions (e.g. slow pyrolysis). Feedstock biomass can include forestry and agricultural waste products, municipal greenwaste, biosolids, animal manures, some industrial wastes such as papermill wastes.
Is all biochar the same?
Key chemical and physical properties of biochar are greatly affected both by choice of feedstock and process conditions (mainly temperature, residence time, heating rate and feedstock preparation). These properties affect the interactions of biochar with the environment of its application as well as its fate. There is no rapid screening technique currently available that provides the means for biochar products to be compared or matched to a particular use.
Pilot biochar reactor located at Gosford
What techniques are currently used to characterise biochar?
The chemical structural aspects of biochar can be characterised spectroscopically (e.g. 13C-NMR, ESR, Raman), chemical/thermal analysis (TGA-MS, Py-GCMS) or microscopically (SEM, TEM). Chemical characteristics of biochar can be assessed using standard agricultural soil testing, although some methods require modification. Ecotoxicological testing such as earthworm avoidance assays and plant germination inhibition assays can be used to test the ecological safety of the biochars.
How stable is it?
Studies of charcoal from natural fire and ancient anthropogenic activity indicate millennial-scale stability. However, the stability of modern biochar products is uncertain: it is difficult to establish the half life of newly produced biochar through short term experiments, and aging processes are expected to affect turnover in the longer term. The limited data available suggest that turnover time of newly produced biochar ranges from decades to centuries, depending on feedstock and process conditions. At the moment there is no established method to artificially age biochar and assess likely long term stability.
Is it safe to use?
Prior to the large-scale endorsement of biochar usage, its safe use with regard to human and environmental health needs to be assured. Pyrolysis systems that meet strict emissions standards have been demonstrated. Some biochars have been tested for toxicity, and found to meet guidelines for dioxins, PAHs and heavy metals, The OECD ecotoxicological test involving response of earthworms has demonstrated lack of toxicity of biochar made from paper sludge. Air emissions from biochar production, and composition of the biochar product, are highly dependent on the production systems and the biomass feedstock. Therefore it is critical that the safety of all proposed facilities is assessed Where biochar is used as a soil conditioner it must conform to relevant Australian and international standards and legislation (e.g . the NSW Protection of the Environment Operations (Waste) Regulation). The “earthworm avoidance test”, an ecotoxicological test method prescribed by the OECD, can be used as an initial environmental test. It is a cheap test that is suitable for developing countries.
What are the agronomic benefits?
A number of studies have been conducted where biochar application has shown significant agronomic benefits. However, these results are not universal as other studies have shown no difference, or even some decline, in productivity. The reason lies in the wide range of properties between different biochars, and variation in impact due to interaction with different soil types. Our incomplete understanding of the processes that occur when biochar is applied to soil limits our ability to predict agronomic impacts of biochars in different situations. There is a need for models to allow extrapolation of location-specific findings by accounting for mechanistic effects of variations in soil type, climate, crop species and pyrolysis feedstock.
Is it economically viable?
The economic viability of biochar is dependent on the price of the product and the benefits to the user. The price will be affected by the cost of feedstock (which may be negative in the case of biomass that would incur a waste disposal fee), and returns from renewable energy generated in the pyrolysis process. Financial benefits to the user may include increased production and reduced fertiliser requirements. Furthermore, the biochar producer or user may benefit from some form of carbon credit under an emissions trading scheme: the producer could receive credit for stabilising organic carbon, avoiding emissions from decomposition; alternatively, the landholder may receive credit for increasing the soil carbon stock in his field where biochar is applied. Thus the economic viability of biochar is influenced by policy; uncertainty over future policy may risk investment in biochar production facilities. The growing cost of waste disposal, and implementation of renewable energy targets, are likely to make the production and application of biochar for electricity and waste management economically viable. Potential returns from carbon trading will be enhanced if biochar is accepted under the Clean Development Mechanism (CDM) of the Kyoto Protocol.
Biochar can help us avoid landfill
What are the environmental and societal benefits?
Models exist for viable agronomic use of biochar in subsistence agriculture. However, appropriate technology and policy needs to be implemented to deal with environmental issues such as methane and particulate emissions, that could contribute to climate change and human health risks. Socio-economic constraints and benefits are not adequately researched. Higher crop yields resulting from biochar applications would be expected to mitigate pressures on land and would also have relevance to land restoration and remediation. Other environmental benefits may include waste re-use and avoided landfill, offset of fossil fuels through renewable energy production, carbon sequestration, potentially reduced soil emissions of non CO2 GHGs, improved crop performance and biomass production.
Source: Australia New Zealand biochar researchers network (ANZBRN)
Above: Dieter Horstman at Byron Eco Park BioChar Seminar.