i
MARISSALAGOYPARENA
SUBMITTEDTOTHEFACULTYOFTHECOLLEGEOF ENGINEERINGANDAGRO-INDUSTRIALTECHNOLOGY
UNIVERSITYOFTHEPHILIPPINESLOSBAÑOS INPARTIALFULFILLMENTOFTHE
REQUIREMENTSFOR THEDEGREEOF
BACHELOROFSCIENCEINAGRICULTURALENGINEERING (MAJOR IN AGROMETEOROLOGY AND FARM STRUCTURES ENGINEERING)
MARCH2010
v
TABLE OF CONTENTS
LIST OF TABLES vi
LIST OF FIGURES vii
LIST OF APPENDIX FIGURES AND TABLES viii
ABSTRACT ix
INTRODUCTION 1
REVIEW OF LITERATURE
Biogas 3
Kitchen waste 4
Anaerobic digestion 6
METHODOLOGY 11
RESULTS AND DISCUSSION
Effects of different treatments on salinity 18
Effects of different treatments on biogas production 19
Changes in daily pH 20
Total solids of feedstock after 30 days of anaerobic digestion 23
First-order Kinetic model 24
SUMMARY AND CONCLUSION 31
RECOMMENDATION 32
REFERENCES 33
APPENDIX 35
vi
LIST OF TABLES
TABLE TITLE PAGE
1 Eight treatments prepared during the experiment 14
2 Mean salinity of eight treatments 18
3 Total biogas production of the eight treatments 19 4 Total solids of the eight treatments after 30 days of anaerobic digestion 24
5 First-order Kinetic values 27
vii
LIST OF FIGURES
FIGURE TITLE PAGE
1 Steps in breaking down organic matter to produce biogas 7
2 Schematic diagram of the anaerobic digester 12
3 Measurement of biogas volume using water displacement method 12
4 Sample of food wastes collected from CEAT-AA Canteen 13
5 Sample homogenized kitchen waste (1:1) 13
6 Cattle manure used as starter 16
7 Layout of the experiment 16
8 Hach Sension5 EC meter used 17
9 Hach pocket pH meter used 17
10 Changes in pH during anaerobic digestion of food waste (mixed) 21
11 Changes in pH during anaerobic digestion of food waste (unmixed) 22
12 Cumulative biogas production of the mixed treatments 25
13 Cumulative biogas production of the 1:2 mixed treatment 25
14 Cumulative biogas production of the unmixed treatments 26
15 Cumulative biogas production of the 1:0.5 unmixed treatment 26
16 Analysis of cumulative biogas production of 1:0.5 mixed treatment using First-order Kinetic Model 28
17 Analysis of cumulative biogas production of 1:1 mixed treatment using First-order Kinetic Model 29
18 Analysis of cumulative biogas production of 1:3 mixed treatment using First-order Kinetic Model 30
viii
LIST OF APPENDIX FIGURES AND TABLES
FIGURE TITLE PAGE
A.1 The sludge after 30 days 36
A.2 Sludge with scum formation 36
TABLE TITLE PAGE
A.1 Physico-chemical characteristics of anaerobic digestion (mixed) 37 A.2 Physico-chemical characteristics of anaerobic digestion (unmixed) 38 A.3 Data of biogas and its corresponding ambient temperature 39 A.4 Total solids of digested food waste after 30 days w/o mixing 40 A.5 Total solids of digested food waste after 30 days w/ mixing 40
ix ABSTRACT
PARENA, MARISSA L., College of Engineering and Agro-Industrial Technology, University of the Philippines Los Baňos, March 2010. “EFFECT OF DIFFERENT FEEDSTOCK CONCENTRATIONS AND MIXING ON ANAEROBIC DIGESTION OF FOOD WASTE.”
Adviser: Dr. Ronaldo B. Saludes
Biogas production of food waste at different feedstock concentrations was determined using laboratory-scale batch anaerobic digesters. A total of eight (8) treatments were used in the study. The treatments were divided into two groups, one is mixed once a day for one minute and the other is unmixed. Each group has four different feedstock concentrations of 1:0.5, 1:1, 1:2, and 1:3 (ratio of fresh weight of feedstock to weight of water). Biogas production, salinity and pH were evaluated to compare the treatments. Biogas volume was measured using water displacement method. Salinity and pH were measured using EC and pH meter, respectively. Food wastes were allowed to digest anaerobically for 30 days. Result showed that feedstock concentration of 1:1 (mixed) produced the highest biogas yield. Unmixed treatments produced negligible volume of biogas. Mixing of feedstock during digestion prevents clumping of starches which slows down hydrolysis as well as the whole digestion process. Results proved that mixing is essential for anaerobic digestion of food waste.
Parameters measured such as salinity and total solids of feedstock at the end of the experiment showed that the digested food waste is not yet fit to be disposed and thus require further treatment.
