Is biochar application always a good strategy to preserve organic matter in agricultural soils? An overview

Size: px

Start display at page:

Download "Is biochar application always a good strategy to preserve organic matter in agricultural soils? An overview"

Blake Andrews
5 years ago
Views:

1 Is biochar application always a good strategy to preserve organic matter in agricultural soils? An overview Claudio Zaccone Dept. of the Sciences of Agriculture, Food and Environment, University of Foggia, Italy (claudio.zaccone@unifg.it) Cesar Plaza Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas, Madrid, Spain Carbon Storage in Soil and Its Role in Supporting Agriculture EXPO, Milan, Italy June 18 th, 2015

2 product?? by-product?? waste?? Biochar is a C-rich product made by the pyrolysis of biomass, with the intention of climate change mitigation and soil quality enhancement (Lehmann and Joseph, 2015). ( Lehmann and Joseph, 2009)

4 n. articles (log scale) 1000 >19,500 before 1995, 53 before 1900 >31,600 >2, Biochar Terra Preta Charcoal in years

Dark Earths (known as Terra Preta de Indio).

5 Surrounding soils Terra Preta 20 cm 200 cm t ha -1 (first 100 cm) One of the basis for the strong recent interest in biochar is that biochar-type substances were found in Amazonian Dark Earths (known as Terra Preta de Indio). Consequently, biochar has been frequently connected to soil management practiced by ancient Amerindian populations before the arrival of Europeans.

Unknown / controversial Empirical evidence of charcoal in soils exists; Liming effect; Carbon storage capacity; High sorption affinity for HOC; Microbial habitat; Increases in mycorrhizal abundance;

and into water systems; Occupational health; etc Empirical (and long-term) evidence is scarce for many modern biochars; C and N cycles; Biochar Loading Capacity; Fate and mobility of biochar;

6 Unknown / controversial Empirical evidence of charcoal in soils exists; Liming effect; Carbon storage capacity; High sorption affinity for HOC; Microbial habitat; Increases in mycorrhizal abundance; Soil Albedo; etc The use of biochar analogues for assessing effects of modern biochars is limited; Soil loss by erosion and compaction; Risk of contamination; Translocation within the soil profile and into water systems; Occupational health; etc Empirical (and long-term) evidence is scarce for many modern biochars; C and N cycles; Biochar Loading Capacity; Fate and mobility of biochar; Availability of contaminants (e.g. heavy metals, PAHs); Effects on native SOM (e.g., priming effect); Soil water retention/availability; Enhanced decomposition of biochar due to agricultural management; Soil CEC; etc

7 ( Xu et al., 2012) Biochar features are extremely variable, depending, e.g., on

8 ( Sharma et al., 2004)

9 ( Sharma et al., 2004)

10 As a consequence, we cannot simply refer to biochar BUT we need to understand that we may face different kinds of biochar!!!

11 biochar(s) soil(s) crop(s) climate(s) agric. practice(s), etc n!!!

13 ?

14 Can biochar substitute natural SOM? Biochar stability and fate e.g., ph, redox conditions, texture, structure, native SOM, biochar (chemical and physical) features e.g., temperature of BC formation, feedstock, stability, ph, occurrence of pollutants, particle size, soil (chemical and physical) features climatic (and biotic) conditions e.g., temperature, precipitations, microbial activity,

15 Can biochar substitute natural OM? How stable is biochar?

17 ( Spokas, 2010)

18 BC stability in soil BC stability in soil BC stability in soil BC stability in soil BC stability in soil BC stability in soil Temperature of pyrolysis Particle size C/O, C/H? etc, pe % clay SOM There are still many open questions about the potential deleterious effect of biochar on native SOM.

19 The addition of new substrates to soil may cause a change in the mineralization of native SOM (i.e., priming effect ). When biochar is added to soils, it may be an ecosystem C source or sink, depending on the nature of the interactions between biochar, microorganisms, and native SOM. microorganism s biochar native SOM Given its porous nature and high affinity for natural OM, it has been hypothesized that biochar is able to sequester non-bc soil OM within its pore network, protecting it from degradation both by microbial enzymes and abiotic oxidants.

21 Some studies have found that biochar may increase mineralization rates of native SOM (e.g., Wardle et al., 2008; Luo et al., 2011; Singh and Cowie, 2014), whereas other studies have found no effects or even negative priming effects (e.g., Liang et al., 2010). Differences in the magnitude and sign of the priming effect depend on soil and biochar type e.g., SOM mineralization tends to be stimulated in soils with low C content treated with biochars produced at low temperatures from grasses instead of woods (Zimmerman et al., 2011).

22 Processes and mechanisms contributing to OM stabilization and destabilization in soils treated with biochar remain largely unknown. Particularly little attention has been devoted to the interaction of biochar with other products used in agriculture to ameliorate soil fertility (e.g., conventional amendments).

In a recent work, we (a) investigated the effects of biochar on SOM pools and (b) examined whether biochar interferes with the stabilization of organic C provided with conventional amendments (i.e., municipal solid waste compost and sewage sludge) co-applied to the soil.

23 In a recent work, we (a) investigated the effects of biochar on SOM pools and (b) examined whether biochar interferes with the stabilization of organic C provided with conventional amendments (i.e., municipal solid waste compost and sewage sludge) co-applied to the soil. We investigated changes in quantity and quality of SOM pools characterized by different protection mechanisms using several chemical, spectroscopic and biological approaches (i.e., elemental analysis, DRIFT, stable isotopes, microbial biomass and activity). ( Plaza et al., Under Review) ( Plaza et al., 2013)

24 Our results show that, after almost 1 year of its application, biochar accumulates mainly in the free SOM fraction, i.e., biochar is mainly located outside aggregates, chemically unaltered and unprotected by the mineral matrix, and secondarily occluded within macroaggregates; biochar promotes C stabilization in soils treated with conventional amendments. We hypothesize that biochar stimulates the microbial transformation of the relatively more labile organic fractions applied with conventional amendments and the sorption of the resultant microbial by-products on soil mineral surfaces. NO significant changes on crop productivity were recorded. ( Plaza et al., Under Review)

25 Today, under EU regulations, biochar (which is not a primary or co-product of a pyrolysis process!) is considered a waste and is therefore regulated by the European Directive on Waste (2008/98/EC) (2003/87/EC on C credits) but if biochar becomes one of our attempts to cover up (bury) failures in energy and environmental management

26 and, in this last case, biochar could become a serious problem for our environment!!!

27 For example, biochar application is expected to improve the overall sorption capacity of soils, and consequently, influence toxicity, transport and fate of trace contaminants, which may be already present or are to be added to soils. Consequently, it has been proposed also as a tool for environmental remediation. ( Li et al., 2014)

28 Nevertheless, while the feasibility for reducing mobility of contaminants in soil might be beneficial, it may result in long mean residence times and accumulation of organic contaminants with potentially hazardous health and environmental consequences. Furthermore, little is known about the short- and longterm distribution, mobility and bioavailability of such contaminants in biochar-enriched soils.

In conclusion, in several European countries, including Italy, biochar must respect national legislations that are not specifically designed for biochar but adopt threshold limits of potential

29 In conclusion, in several European countries, including Italy, biochar must respect national legislations that are not specifically designed for biochar but adopt threshold limits of potential analogous material (sewage sludge, amendments, etc). When it could potentially be applied to soil as amendment, ph may be a limiting factor, especially in the South of Europe and in Mediterranean conditions.

Can biochar replace soil OM always and everywhere? chemical structure? stability? contaminants? etc definition? still several open questions!!! surface and porosity? CEC?

30 Can biochar replace soil OM always and everywhere? chemical structure? stability? contaminants? etc definition? still several open questions!!! surface and porosity? CEC? hydrophobicity? mineral interaction? etc soil flora and fauna? pathogens? biodiversity? etc C storage? soil fertility? crop yield? cycle of nutrients (e.g., N)? erosion? GHG emission? soil water? etc

31 Thanks for your attention

The Case for Biochar. Annette Cowie, Bhupinderpal Singh Lukas Van Zwieten

The Case for Biochar. Annette Cowie, Bhupinderpal Singh Lukas Van Zwieten The Case for Biochar Annette Cowie, Bhupinderpal Singh Lukas Van Zwieten Amazonian Terra preta Terra preta (dark earth) soils High plant productivity High organic carbon stable char (black carbon) Source: