Optimising Sugarcane Trash Management for Biofuels Production in Australia and Brazil

Transcription

1 Optimising Sugarcane Trash Management for Biofuels Production in Australia and Brazil L. CERQUEIRA 1, L.A. EDYE 2, M.K. WEGENER 3, F. SCARPARE 4 and M.A. RENOUF 5 1 Queensland University of Technology, Brisbane, Australia 2 BioIndustry Partners, Gold Coast, Australia 3 University of Queensland, Brisbane, Australia 4 CTBE, Campinas, Brazil 5 Life Cycle Strategies, Brisbane, Australia BioIndustry Partners

2 Sugar/Ethanol/Electricity Australia Sugar million tonnes 2 nd or 3 rd largest raw sugar supplier to world market Ethanol - 60 million litres Electricity ca. 1% market share Brazil Sugar - 35 million tonnes Ethanol - 21,700 million litres Electricity ca. 6% market share (?)

3 Whole crop harvesting potentially doubles surplus biomass but requires significant changes to the industry value chain and substantial investment

4 Agro-industrial sustainability criteria The greenhouse gas balance of the production chain is positive The biomass production is not at the expense of carbon sinks in existing vegetation and soil The biomass production does not endanger the food supply and existing local business activity (i.e. local supply of energy, medicines and building materials) The biomass production has no impact on biodiversity (protected or vulnerable biodiversity is not affected or if possible strengthened) Soil and soil quality are retained or improved Ground water and surface water are not depleted and water quality is maintained or improved Air quality is maintained or improved Enduring profitability that contributes to local prosperity and to the social wellbeing of employees and the local population. Framework Convention on Climate Change & the World Bank Carbon Fund

5 Billet cane 70% Trash (leaves & Tops) 23% Root stock 7% Trash impacts Soil moisture Soil nitrogen & carbon Erosion prevention Nitrous oxide emissions

6 Many layers to this issue Trash resource & agricultural practice Cane varieties & breeding programs Climate & soil types Mineral fertilizer amount & timing to offset trash removal Harvesting methods Whole cane w/w out compaction, second pass Intensification factor or average transport distance Processing options Separation of cane & trash or whole milling Crystalline sugar?, boiling schemes Energy efficiency Boiler pressures, electricity generation Products (other than sugar, conventional ethanol & electricity) Embodied emissions & energy of products versus petroleum based alternative Policy

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8 Approach - Integrate APSim, process material balance model and SimaPro Tillage Crop Growth Simulation AP- Tractor Fuel use Environmental Impact Simulation (LCA) SIMAPro Climate data Rain fall Evaporation Temperature Fertiliser (N,P,K,S) Electricity Water Product: 100 T cane Land use change: Inputs from technosphere: Fuel Radiation Fertiliser GWP Soil Pesticides NRT Organic matter (N) Nitrification Bulk density Fertiliser (N) Irrigation Water Trash removal Cane yield Residue yield N Losses (C:N) Soil Carbon Water losses Emissions Air Emissions Water Emissions Soil Acidification Eutrification APSIM - Provide a means of predicting plant performance and crop yield beyond the bounds of experience and experimentations SimaPro - LCA tool to predict the environmental impacts across the entire life cycle of products from cradle to grave Farm Data FEAT (Economic Model )

9 Comparison of farming inputs Parameter Units Australia Brazil Energy inputs Diesel for tractors MJ/t Diesel for harvesting MJ/t Fertilizers and agricultural chemicals Urea (as N) kg/t Phosphate (as P 2 O 5 ) a kg/t Potassium chloride kg/t Limestone kg/t Pesticides active ingredients g/t Transport of cane to mill Rail t.km Road t.km Production of capital goods Tractor kg/t Harvester kg/t Other agricultural machinery kg/t a Diammonium phosphate in Australia, single superphosphate in Brazil

10 APSim outputs

11 APSim estimates of nitrous oxide emissions Reasonable agreement with field measurements Higher than predicted by other agricultural models Higher than values used in greenhouse gas accounting Thorburn et al N 2 O = 289 x GWP of CO 2 nothing to laugh about!

12 Sugar Biorefinery material balance Sugarcane Biorefinery Model Factory seperation of cane & trash Sugar Australia Tonnes Cane supplied % mass Tonnes Cane to mill Tonnes Juice Tonnes Raw sugar 55,988 Juice to sugar Sucrose 55,596 Tonnes of cane billets 1,000,000 Cane to mill 940,800 Sucrose 61,128 Water 280 Sucrose 135,000 Sucrose 125,582 Impurities 10,378 Impurity 112 Soluble impurities 22,629 Soluble impurities 21,229 Water 361,761 Molasses expor 50% Tonnes Fibre (db) 135,000 Fible (db) 125,874 Juice directly to ethanol Final Molasses Australia Tonnes Molasses 11,284 Ash 30,000 Ash 34,164 Sucrose 61,128 Molasses 22,568 Sucrose 2,766 Water ,371 Water 633,951 Impurities 10,378 Sucrose 5,532 Soluble impuities 5,133 Water 361,761 Soluble impurities 10,266 Water 3,385 Other fermentables 2,528 Delivered trash % mass Tonnes Trash to biorefinery Tonnes Bagasse Tonnes Water 6,770 Fibre 125,874 Bagasse & trash resourtonnes Tonnes of trash 90,000 Tonnes of trash 149,200 Water 125,874 Fibre 173,910 Sucrose 270 Sucrose 9,688 Sucrose 2,800 Water from sugar manufacture Tonnes Water 202,594 Soluble impurities 1,530 Soluble impurities 2,930 Soluble impurities 473 water 354,711 Sucrose 12,487 Ash 2,700 Ash 11,826 Ash 28,241 Soluble impurities 3,404 Fibre (db) 52,200 Fibre (db) 48,036 Ash 40,067 Water ,300 Water 76,720 Total biomass 432,462 Filter cake Tonnes Non-sucrose solids 6,058 Mill inputs Tonnes Sucrose 527 Water (from recycle) 235,200 Water 19,755 Enzymes (dextranase & amylase) 2.40 Nitrogen 5,43 Lime Phosphorus 2,63 Water to effluent treatment Tonnes Phosphate 0.00 Water 119,511 Heater cleaning Sucrose? Flocculent 3.58 Impurities? Antiscale 3.76 Antifoam 6.12 Ethanol from juice and/or molasstonnes Sucrose 63,894 Conventional ethanol Inp Tonnes non-fermentable Impurities 12,413 Ammonium Sulphate Total fermentables (as glucose equivqlents) 70,354 Diammonium Phosphate Stoichiometric ethanol yield 35,951 Sulphur Dioxide Actual ethanol yield 32,715 Sulfiric acid Actual CO 2 yield 31,253 Soda Yeast production (db) Chemicals Inorganic Water from juice and/or molasses 361,783 Chemicals Organic Water make up 0 Lime Yeast Conventional distillery outputs Hydrous ethanol (denatured?) Vinasse Nitrogen Phospherous Yeast cream Waste water Initially - bagasse & trash resource to ethanol or electricity. Advances biofuel based on data in the NREL Design report because it is both detailed and transparent. End game can you harvest trash to produce lignocellulosic ethanol or electricity & obtain favourable LCA outcomes?

13 Boundary System(LCA) Functional unit Tonnes of cane Cavalett et al. (2011) MJ fuel

14 Stationary power generation Australia Hydro electric % Wind % Biomass % Other % TOTAL RENEWABLE % Brazil Hydro electric - 82 % Biomass - 6 % Other -? TOTAL RENEWABLE - ca. 89 %

15 The future of the project OUTPUTS Field to wheel LCAs for conventional + advanced ethanol production in Australia & Brazil under a number of scenarios that include whole and partial trash harvesting CRITICAL FACTORS Water availability Apparent nitrogen use & timing of fertilizer application Energy mix Policy & cost of coal v oil PROBLE OUTCOMES In Australia whole cane harvesting may be sustainable but the best use for the biomass resource is likely to be electricity generation In Brazil whole cane harvesting will be sustainable and the best use for the biomass resource will be advanced biofuels production (or other products that replace petroleum based products)