I have a question about biomass: in new Caledonia it could be possible to use biomass for biogas production, but because of the particular soil rich in nickel ores, the biomass contains high concentration of such metal. If the digestate was used as fertilizer, the soil used for agriculture would be heavily contaminated. Do you know if the biomass can be treated in advance for reduction of Ni and, if so, what technology can be used?
Heavily contaminated soil may not be recommended for agriculture but can be of an interesting research subject for people interested in phytoremediation studies. COntaminated soils could be used for floriculture
Nickel will be most problematic when the soil is in an acid condition. The area of high nickel might be suitable for cultivation if the pH was maintained at near neutral pH. If the nickel is concentrated tillage might be able to disperse the zones which are problematic. Many areas of toxic metals respond to additions of compost. If biomass can be produced the use of the biomass for biochar production can be used to produce clean energy and the char can be a liming agent effective for the remediation of acid red soils with heavy metal issues because of alkaline nature of these chars especially when they are produced at elevated temperature. Biochars have been most effective on old red ultisols and oxisols.
@ Eric D van Hullebusch
Dear Eric,
it s difficult that they have such value, anyway it was asked them.
To be honest I don't think it is possible to pre-treat bomass to reduce the Ni content...how to do that? with water? acid? The biomass will be very acid after such leaching and maybe will became like glop. The only possibility would be the scattering on a great surface of fields, in order to reduce the concentration of Ni. Otherwise one should try to precipitate Ni in the liquid digestate by lime for instance. What do you think, according to your experience?
Thank you very much
Hello Francesco,
Did you try some agromining's books/ paper? They should have some technic could help you in this.
However, in this first moment, lime is more cheap and easy to use.
The biomass should be previous treated with a mineral acid (HNO3 is most suitable). In this way, most of metal ions retained on biomass can be released, and the acid-treated biomass is poor in such metal ions.
I think treating with 0.1 N HCl for few hours will do. It is supposed to remove most heavy metals present in the biomass or the soil used. But you must first know if the biomass you're working with can tolerate that concentration and remain viable.
This is a reference that might help
Yang, J. & Volesky, B. (1999). Removal and concentration of uranium by seaweed biosorbent. Process Metall, 9, 483-492. https://doi.org/10.1016/S1572-4409(99)80137-0
Amend with microbes that posses nickel affinity to immobilize the metal ions or inhibit mineralization and possibly convert into complex salts
Since the biomass carries such a lot amount of metal, a treatment using acid might be suitable for leaching all metal content from cell.
A further treatment to the metal containing acid can be carried out using ph adjustment to achieve metal separation.
This method might be expensive to be used in a large amount of biomass. But i think this is the most proper way to be applied, based on my limited knowledge.
Legacy Biosolutions has a product using probiotics CLEAR (water) and FOUNDATION ( for soils) which may be tested to reduce the metals. The issue that you are describing is also prevalent in fish farming when toxic aquaculture waste is used for fertilizer without an intermediary step of composting. Aquaculture waste prior to composting with probiotics allows toxic unstable reactive metals to contaminate soils when the waste is used as uncomposted fertilzer.
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