Life Cycle Assessment of biogas production process from Laminaria digitata

Transcription

1 Life Cycle Assessment of biogas production process from Laminaria digitata Merlin Alvarado Morales Bioenergy Research group Department of Environmental Engineering Technical University of Denmark

2 .\Agenda to be followed... \Introduction... \Objective... \LCA framework... \ Goal and scope definition Inventory analysis (LCI) Impact assessment Interpretation \... \ Conclusions 2

3 .\Introduction Objective The aim of this work was to perform a Life Cycle Assessment (LCA) of a biogas process from Laminaria digitata to identify bottlenecks and to improve the environmental aspects at various points in its life cycle. 3

4 o ISO (ISO 2006) o ILCD Handbook (EU-JRC-IES, 2010) 4

5 Goal and scope definition o Functional unit o System boundaries o Assumptions and limitations o Impact categories 5

6 Inventory analysis (LCI) o Inventory of flows from and to environment o Inputs of water, energy, and raw materials o Outputs to air, land, and water o Data flows are related to the functional unit 6

7 Impact assessment o Selection of impact categories (global warming, eutrophication, etc.) o Selection of characterization models o Impact measurement 7

8 Interpretation o Identification of significant issues o Evaluation of the study... \ Completeness... \ Sensitivity analysis... \ Consistency check o Conclusions, limitations and recommendations 8

9 Goal and scope definition Cultivation and processing of one tonne of dry seaweed biomass Laminaria digitata produced in Denmark for biogas production. Functional unit 9

10 Goal and scope definition To assess the potential environmental impacts of a seaweed-based biogas process as well as to identify hotspots in the life cycle where environmental performance of the system can be improved. 10

11 Goal and scope definition o The impact assessment was performed based on EDIP2003 (Hauschild and Potting, 2003). o Impact categories: Global warming, Acidification and Terrestrial Eutrophication. 11

12 Goal and scope definition System boundaries process system description 12

13 Goal and scope definition o The investigated algae processing system was assumed to be located along the coastline in Denmark. o The seaweed cultivation site was situated at the open sea. o The biogas production facility was situated at the seaside on land. Assumptions 13

14 Goal and scope definition o The biogas produced is combusted in a gas engine with electrical efficiency of 42%. o Heat is also cogenerated but used internally in the biogas plant. o The electricity generated is assumed to substitute coal-based marginal electricity. Assumptions 14

15 Goal and scope definition o The digestate generated is used as fertilizer on agricultural land. Assumptions 15

16 Inventory analysis (LCI) Samples of L. digitata were collected in late March 2011, at Ømo, Denmark. Arbona and Molla (2006) and Edwards and Watson (2011), personal communication with fishermen Seaweed production 16

17 mlch4/gvs.\lca framework Inventory analysis (LCI) Data on biogas potential were generated through batch experiments at 52 C for 30 days S. latissima* L. digitata* P. palmata* U. lactuca** U. fusca** Anaerobic digestion 17

18 Impact assessment o The impact assessment was facilitated in SimaPro LCA software (Pre, 2010). Assumptions 18

19 Impact Potentials.\LCA framework Impact assessment 200 Characterized Environmental Impact Potentials Seaweed Production (SWP) Mechanical Pretreatment (MP) Anaerobic Digestion (AD) Total Global Warming (kg CO 2 -eq) Acidification x 10 (m 2 ) Terrestrial Eutrop. x 10 (m 2 ) Assumptions 19

20 Interpretation o Important benefits for all impact categories due to savings linked to both the avoided fertilizer and energy production. o In fact, 555 kwh of electricity per functional unit are recovered and delivered to the grid, thereby displacing coal-based marginal electricity production somewhere else in the energy system. Assumptions 20

21 Interpretation o Electricity consumption was estimated to be: 118 kwh per one tonne of dry seaweed. o Electricity production was estimated to be: 555 kwh per one tonne of dry seaweed. o Net electricity production: 437 kwh per functional unit. Assumptions 21

22 Interpretation o Electricity, hard coal, at power plant/nordel S : kg of CO 2 per kwh of electricity produced. o Therefore, ca. 372 kgco 2 per tonne of dry seaweed are avoided. o 8, 9 and 37 kg of N, P, and K per one tonne of dry seaweed. Assumptions 22

23 Impact Potentials Sensitivity analysis Sensitivity Analysis Results Base case S1 S2 S3.\LCA framework Global warming (kg CO2-eq) Acidification x 10 (m2) Terrestrial Eutrophication x 10 (m2) S1: Energy consumption in SWP (-10%) S2: LCH4/gVS (+10%) S3: LCH4/gVS (+42%) -900 Assumptions 23

24 Conclusions o Sensitivity analysis showed that the system has potential for technological development and consequently significant improvements. o Improve the biodegradability of the feedstock by different pretreatments. o Metal content in the digestate needs to be evaluated. 24

25 Life Cycle Assessment of biogas production process from Laminaria digitata Merlin Alvarado Morales Bioenergy Research group Department of Environmental Engineering Technical University of Denmark

26 Inventory analysis (LCI) Resource Seaweed Mechanical Anaerobic Unit consumption production pretreatment Digestion Diesel L 30 Petrol L 30 Electricity kwh Heat kwh (GJ) 512 (1.84) Water L Stock nutrients solution L 0.03 Plantlet nutrients g

27 Conclusions o Production of different biofuels has their own benefits, risks and uncertainties. 27

28 Conclusions o In order to ensure net societal benefits of biofuel production, governments, researchers and companies need to work together to carry out comprehensive assessments, map suitable and unsuitable areas, and define/apply standards relevant to the different circumstances of each country. 28