A COMPARATIVE LIFE CYCLE ASSESSMENT OF ROCK BASED AND RECYCLED P - - PDF document

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A COMPARATIVE LIFE CYCLE ASSESSMENT OF ROCK BASED AND RECYCLED P FERTILISERS

Fabian Kraus, Kompetenzzentrum Wasser Berlin gGmbH fabian.kraus@kompetenz-wasser.de www.kompetenz-wasser.de

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Overview

• Conventional fertilizer production
• Recovery from wastewater path and comparison
• Outlook

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Overview

• Conventional fertilizer production
• Recovery from wastewater path and comparison
• Outlook

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Conventional fertilizer production

Nitric acid Electricity Water Heat Additives

Phosphate rock, Calcium phosphates Single super phosphate (SSP) and PK-fertilizer Triple super phosphate (TSP) NP-, NPK-fertilizer

via ‚nitro phosphate route‘ and by-products

NP-, NPK-fertilizer

via ‚mixed acid route‘

Mono ammonium phosphate (MAP) Di ammonium phosphate (DAP) Phosphoric acid (and phosphogypsum) Nitro phosphoric acid Phosphate rock beneficiated Phosphate ore

Electricity Water Heat Diesel Additives Sulfuric acid Electricity Water Heat Additives Sulfuric acid Electricity Heat Potassium salts Electricity Heat Electricity Heat Ammonia Electricity Heat Ammonia

0-21-0*/* 0-21-0*/* 0-48-0* 0-48-0* 11-52-0 11-52-0 18-46-0 18-46-0

Electricity Heat Ammonia AN/ Nitric acid Potassium salts

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Electricity Heat Ammonia Potassium salts

0-36-0* 0-36-0*

Raw materials Intermediates Final products/fertilizer

also AP

* Variable nutrient concentrations

+ Calcination + Solvent-extraction

2 % SSP: 0.5 % PK: 7.5 % 5 % 5 % 56.5 % NP: 4 % NPK: 7.5 % NP: 4.5 % NPK: 7.5 %

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Goal and scope of LCA

Goal: Environmental impact assessment of conventional P- fertilizer production and application Function: Provisioning of conventional P-fertilizers and their agricultural application Functional unit: Functional equivalency is derived via nutrient content, meaning functional unit is „per kg P2O5 in the fertilizers (total phosphate content)“ In case of multi nutrient fertilizers, efforts for other nutrients (N, K) are allocated

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Scope, System boundaries

System boundaries

Emissions to air Emissions to water Waste and emissions to soil Chemicals Energy

(Electricity & Heat) Fossil fuels Transportation Materials, Infrastructure Phosphate

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Mining & beneficiation Phosphate rock Acid and fertilizer production Nitro-P AP SP/PK H3PO4 NP/NPK Fertilizer application Crude oil/ Natural gas Sulfur Heavy fuel oil/ Natural gas Sulfuric acid Ammonia, Nitric acid Potassium chloride Sylvinite

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Relevant countries of origin for phosphate rock and transportation routes

[1] Google

[1] Google Maps 2018

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Take home messages: #1 Sulfuric acid production and potential by-product valorization are important #2 Valorization of by-products (CAN) reduces energy footprint

Non-renewable cumulative energy demand (CED) coal, oil, natural gas, uranium

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Take home messages: #3 GWP of 1 kg N production and application 6-fold higher than for 1 kg P2O5 #4 GWP for N in half equally related to production and to application

Global warming potential (GWP) fossil CO2, CH4, N2O

1 kg P2O5 & 1 kg N

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Human toxicity potential (HTP) heavy metals in agricultural soils

Take home messages: #5 Fertilizer application dominates human toxicity potential #6 Extreme variation of HTP depends on Cd-content of phosphate rock

igneous rock average Cd-polluted sedimentary rock sedimentary rock with high Cd-content

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Take home messages: #7 P and heavy metal emissions into environment of importance #8 Minor efforts for decadmiation technologies compared to benefits

Normalized results

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Summary

• NP-/NPK-production via nitro phosphate route shows lower efforts for

almost all impact categories related to P2O5

• Production route and origin of sulfuric acid is very important for energy-

and SO2-footprint (+/- 40 %)

• P-fertilizer application shows high normalized shares regarding the

freshwater eutrophication potential and the human toxicity potential

• Decadmiation of sedimentary phosphate rock reduces human toxicity

potential significantly, while the additional increase in energy demand and CO2-footprint are moderate

• (Long term-)emissions from gypsum stacks may be problematic

(potential local environmental drawbacks for the aquatic environment) 11 12

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Overview

 Conventional fertilizer production

• Recovery from wastewater path and comparison
• Outlook

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Goal and scope of LCA

Goal: Environmental impact assessment of P-fertilizer recovery from wastewater path and its application Function: Treatment and disposal of primary and excess sludge

• f a typical large scale WWTP in Germany

Functional unit: All efforts/ benefits of an additional P recovery technology are related to the system and its function, the functional unit is „changes on sludge treatment and disposal per p.e. and year“

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Scope, System boundaries

System boundaries

Emissions to air Emissions to water Waste and emissions to soil Fertilizer application Digestion Mono- incineration Ash disposal Static thickening WWTP (simplified) Chemicals Energy

(Electricity & Heat) Fossil fuels Transportation Materials, Infrastructure Recovered P- fertilizers Recovered P- fertilizers Mechanical thickening Dewatering Primary sludge Excess sludge T T Substitution of conventional fertilizers (Average German P) Substitution of conventional fertilizers (Average German P)

3x Struvite precipiation from digested sludge 5x Struvite precipitation from centrate 4x Recovery from ash

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Non-renewable cumulative energy demand (CED) coal, oil, natural gas, uranium

Take home messages: #1 Reduced sludge volume and gas production improve energetic efficiency #2 High-value (by-)products from ash improve energetic profile of processes

Trade-off: electric efficiency of CHP vs. mono-incineration Considering technical P-acid as product

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Global warming potential (GWP) fossil CO2, CH4, N2O

Take home messages: #3 Direct emissions of mono-incineration (N2O) of importance #4 Quitting lignite incineration (and co-incineration) reduces GWP severely

• approx. + 13 kg CO2-Eq/(pe a)

if co-incineration is status-quo

• approx. + 9 kg CO2-Eq/(pe a)

for N2O-emissions mitigation

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Human toxicity potential (HTP) heavy metals in agricultural soils

Take home messages: #5 Struvite and technical P-acid are products with negligible contaminant-level #6 Sludge ash contains high HM-loads, HM removal recommended

Reduction Cd-Input Metals from sludge/ ash

igneous rock sedimentary rock with high Cd-content

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Summary

• Integrated P recovery in WWTP (struvite recovery) reveals

environmental benefits (for EBPR WWTP), it is accompanied by

• perational benefits (e.g. reduced sludge volume due to improved

dewatering)

• End-of-pipe P recovery from sludge ash can be energetically and GWP-

related more or less equal to a conventional P fertilizer production, if chemical consumption can be reduced via internal recycling and high value products and by-products are recovered

• Strong differences regarding toxicity indicators for products derived

from sludge ash dependent on the fate of heavy metals in the process

• Consideration of local boundary condition (EBPR/ sludge disposal route)

necessary for an environmental friendly P-recovery scheme

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Overview

 Conventional fertilizer production  Recovery from wastewater path and comparison

• Outlook

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Outlook

Products Precipitates (struvite and

• ther salts) from sludge

and centrate Conventional intermediates (H3PO4, Ca3(PO4)2) from sludge ash Sludge ash and thermal recycled phosphates or processes mixing ash with acids Outlook and further development Processes with 50 % P- recovery rate in development Full-scale implementation pending, first plant under construction Full-scale implementation pending Product quality regarding contaminants Heavy metals and organic pollutants negligible Heavy metals negligible,

• rganic pollutants

destroyed by incineration Heavy metals relevant,

• rganic pollutants

destroyed by incineration Market potential Niche market, costs can be justified via operational benefits, marketing can create additional income Main market, implementation of products in conventional production processes possible, costs for recovery have to be financed via product sales

• r via sewage fees

Niche market, costs for recovery have to be financed via product sales

• r via sewage fees, end-of-

waste status depends on conformity with new FPR

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Thanks for your attention!

 Conventional fertilizer production  Recovery from wastewater path and comparison  Outlook

• Questions?

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