Beyond Biorecovery: environmental win-win by biorefining of metallic wastes into new functional materials

The last 30 years' research on metal biorecovery from wastes paid scant attention to the strong CONTEMPORARY demands for (i) conservation of dwindling vital resources (e.g platinum group metals (PGM) and, recently rare earth elements, (REE), base metals and uranium) and (ii) the unequivocal need to extract and refine them in a non-polluting, low-energy way.
On the other hand, 21stC technologies increasingly rely on nanomaterials as these have novel properties not seen in bulk materials. Bacteria can fabricate nanoparticles, bottom up, atom by atom, with exquisite fine control offered by enzymatic synthesis and bio-scaffolding that chemistry cannot emulate. Bio-nanoparticles have proven applications in green chemistry, low carbon energy, environmental protection and in, potentially, photonic applications (e.g. nano-Au). Bacteria can be grown scalably and cheaply, i.e. step changes in facile production, scalability and price.
Recent work showed the ability of bacteria to make these nanomaterials from primary and secondary wastes, yielding, in some cases, a metallic mixture which can show better activity than 'pure' nanoparticles. Fabrication of structured bimetallics can be hard to achieve by chemical means.
For some metals like REEs and uranium their biorecovery from wastes (U) and scraps (REE) into bulk crystalline minerals can make 'enriched' solids for delivery into further commercial refining to make new magnets (REEs) or nuclear fuel (U). Biofabricating these solids is beyond the ability of living cells although biogenic nano-uranium phosphate can be used to 'hoover' base metals (and radionuclides) with a capacity several orders of magnitude greater than commercial ion exchangers.
This project will operate at several levels of complexity, maturity and risk. Base metal mining wastes (e.g. Cu, Ni) will be biorefined into concentrated sludges for chemical reprocessing or alternatively for evaluating the scope to make base metal-bionanoproducts. U-mining waste will be biorefined into phosphate minerals for commercial fabrication into nuclear fuels. Precious metal wastes will be converted into bionanomaterials for catalysis and energy applications.
In all of these examples the environment will be spared the dual impact of both the primary source pollution and the high energy demand of processing from primary 'crude'.
Metallic scraps present problems as they require strong acids for dissolution. Approaches will include the use of acidophilic bacteria, use of alkalinizing enzymes or using bacteria to first make a chemical catalyst (under benign conditions) which can then convert the target metal of interest from the waste leachate into new nanomaterials (a hybrid living/nonliving system, already proven).
The interface between biology, chemistry, mineralogy and physics, exemplified by nanoparticles in their unique 'biochemical nest', will receive special attention as this is where major discoveries are to be made; hence cutting edge technologies (e.g. X ray microscopy with nanoscale elemental mapping) will be applied in order to relate structure to function, and validate the contribution of upstream waste amendment, doping or 'blending' to these, as well as novel materials processing already shown to increase bio-nanoparticle efficacy.
Secondary wastes to be 'scoped' for biorefining will include magnet scraps (REEs), spent automotive catalysts, road dusts (precious metals, Fe,Ce) and electronic scrap (Cu, precious metals). Their complexity and refractory nature makes for a higher 'risk' than with mine wastes but the 'payoff' compensates, in that the volumes tend to be lower, and the potential for 'doping' or 'steering' to fabricate/steer engineered nanomaterials is correspondingly higher.
The B3 project will have an embedded significant (~15%) Life Cycle Analysis assessment of the systems chosen for special focus, and end-user trialing following scoping studies in conjunction with an industrial platform.

CO2 and Energy: It is hard to 'value' CO2 ; this requires embracing the social/environmental 'costs' as opposed to just pure economic factors (Clarkson & Deyes H.M.Treasury working paper 140, 2002). The IPCC consensus of $9-$197/tonne CO2, is upheld in that report; a mean value of ~ $100/t is taken.

For Umicore (Belgium: a typical smelter) processing (2004) 6430t secondary materials gave 0.4t Pt, 0.5tPd and 0.1t Rh and CO2 emission to air of 2207.5 t. (Saurat, 2006), or a CO2 'value'/t metal of $2207.5(100) = $220,750. If we save just 1% of this CO2 and assume 100 similar refineries worldwide the 'value' of biorefining p.a. is $220,750, or $2.2M in 10 years. Assuming 10% market penetration over 100 yrs (other factors assumed constant) that makes:

$2.2B.

The corresponding energy consumption (Umicore) was 64 TJ (additional CO2 burden of electricity produced into Grid) and hence considerable power savings would be made by reduced energy consumption, also calculable as CO2 equivalents.

Mining: the total est. global CO2 emissions (kt CO2 equivalent) are: Cu: 52,466; Au, 31,298; Ag, 8,069; Fe, 8,011, Zn, 5,384 Pt 3,204, Pd 2,237: (source Material Security Report, Resource Efficiency KTN); a total of 110699 kt, at an estimated. 'value' in CO2 of 110699(1000)(100) =

$11B

In our report (Royal Society: Brian Mercer Senior Award for Innovation 2008; on request) on the economic potential of making electricity from fuel cell bionanocatalyst with precious metals biorefined from 10,000 t road dust was calculated from real data (factoring-in the cost of biomass production and the cost of making fuel cells) as follows:

Value of precious metals recovered (2008 prices) £356,000
Assuming all of that metal went into making PEM fuel cells (3,865 1 kW FCs)

Value of electricity made at 2008 prices = £6M (i.e. what you pay) (£0.18/kWh)
Value if sold to Grid at 2008 price (i.e. what you supply) (£0.04/kWh) = £1.3M

But (since 2010) we have feed in tariffs and electricity is sold from microgenerators to utilities at a typical market rate of ~ 5 p/kWh. The value above now becomes

£6M + 20% of £6M = £7.5M

Better oil extraction: One application of biorefined materials is in heavy oil upgrading; our economic calculations were ratified by J. Levie (see letter) and EPSRC referees (see also Petrobank letter).
Calculated extra oil with catalyst (billion barrels) is 200,000 bbl/y/well.
Profit/barrel = $40 (£25) = £5M
50 mg catalyst/barrel; total needed = 10 kg
Road dust total/yr = 250,000 t
Catalyst available/yr = 200 kg
Annual potential profit just from UK derived road dust = £4.75 M
Assume UK generates 1/100 of total global recoverable road dust; potential profit in 10 years from just Petrobank facilities =

£4.75 B

Green Chemistry: Market research from Catalytic Technology Management Ltd (for heterogeneous metal catalysts), highlighted particular niches for Bio-catalysts in synthesis of platform chemicals (higher product selectivity, hence less waste (as we showed)). Of particular note is where there is currently no good commercial catalyst e.g. Au/Pd which is excellent in selective oxidations with major applications in (e.g.) the fragrances market.

Tomorrows spin technologies: Our recent findings (published, 2012) show the surface of Bio-Pd nanoparticles (unlike chemical equivalent) to be electron spin polarised- bringing novel applications in chirality (product selectivity: elusive in chemical technology) as well as potential applications like liquefaction of H2; the cost of H2 is the single limiting factor for the Hydrogen economy (Brian Mercer Economic Report: above). Liquifaction is energy-expensive; improvements here would impact on market price of H2.

Base and rare earth metals and uranium: Prices of these are rising steeply, with major geopolitical issues regarding materials supply/security. Recovery from wastes/ resource recycling are inescapable on socio economic & pollution grounds