• 1997-1998: Conducted a research to ascertain the influence of straw and byproducts of biogas as fertilizer materials on the growth and development of the rice plant.
• 1998 January–2002 November: Conducted several researches to assess biogas liberation from different raw materials and methods to increase the efficiency of gas liberation statistics of batch type biogas digester.
• 2005-2010 April Served as a teaching assistant and research assistant for the Department of Environmental Sciences and Technology in the Faculty of Agriculture University of the Ryukyus, Japan.
• 2002-2004: conducted a Research project on assessment of biogas liberation efficiency of market garbage as an alternative energy and to compensate bio fertilizer needs funded by environment ministry.
• 2003-2004: Served as the principal investigator to the research project funded by Council for Agricultural Research and policy (CARP) on “Development of a two phase straw biogas digester and its performance evaluation.
• 2003-2004: Principal investigator of the Climatic Change project funded by the Environmental Ministry.
• 2004-2010: Conducted researches related to waste managements, land reclamations and environmental science in the University of the Ryukuys, Japan.

• G.Y.Jayasinghe, Y.Tokashiki & M.Kitou (2005) “Development of synthetic light weight soil aggregates utilizing coal fly ash and mine clay as waste materials”:Journal of Tropical Agricultural Research and Extension (TARE):ISSN 1391- 3646), 2005 (8), 1-12:University of Ruhuna, Matara,Sri Lanka.
• G.Y.Jayasinghe & Y.Tokashiki (2006) “Utilization of coal fly ash for the production of artificial aggregates as a crop growth medium with acidic “Kunigami Mahji” soils in Okinawa-Japan”; Journal of Solid Waste Technology and Management (ISSN:1088-1697),2006:32(1),1-9:Widener University, 1,University place, Chester, Philadelphia (19013-5792), USA.
• G.Y.Jayasinghe, Y.Tokashiki & M.Kitou (2008) “Characteristics of synthetic soil aggregates produced by mixing acidic “Kunigami Mahji” soil with coal fly ash and their utilization as a medium for crop growth”: Journal of Soil Science and Plant Nutrition.. 2008(54), 264-276. ISSN:0038-0768,Doi:10.1111/j.1747-0765.2007.00229.x.
• G.Y.Jayasinghe, Y.Tokashiki , M.Kitou & K.Kinjo (2008) “Oil palm waste and synthetic zeolite : an alternative soil-less growth substrate for lettuce production as a waste management practice”. Journal of Waste Management and Research. 2008(26), 559-565. ISSN: 0734-242X. DOI:10.1177/0734242X08090046.
• K.Kinjo, Y.Tokashiki, M.Kitou, K.Sato, G.Y.Jayasinghe & F.Anugroho (2008). “Organic and Inorganic Composition of Floating Materials on Surface Water of River in Mangrove Forest”. Journal of Clay Science. 2008:47 (3) 114-120.
• G.Y.Jayasinghe, Y.Tokashiki, M.Kitou & K.Kinjo (2009). “Coal fly ash based synthetic aggregates as potential alternative container substrates for ornamentals”. Journal of Plant Nutrition and Soil science, 172(5), 720-728. ISSN: 1436-8730. Doi:10.1002/jpln.200700296.
• G.Y.Jayasinghe, Y.Tokashiki & M.Kitou (2009). “Evaluation of coal fly ash based synthetic aggregates as a soil amendment for the low productive acidic red soil”. Journal of Water Air soil Pollution. 2009(204), 29-41).Doi: 10.1007/s11270-009-0023-y.
• G.Y.Jayasinghe, Y.Tokashiki & K.Kinjo (2009) “Recycling of coal fly ash and paper waste to improve the low productive red soil in Okinawa, Japan’.2009, 37(9), 687- 695. Journal of clean soil air water. DOI: 10.1002/clen.200800177.
• K.Kinjo, Y.Komiya,Y.Tokashiki, M.Kitou,G.Y.Jayasinghe & F.Anugroho (2009). “White crystal material developed from the Shimajiri mudstone in Okinawa islands, Japan”. Journal of Clay Science. 48 (3), 131-136.
• G.Y.Jayasinghe, Y.Tokashiki & M.Kitou (2010). “Use of synthetic soil aggregates as a containerized growth medium component to substitute peat in the ornamental plant production”. Journal of Archives of Agronomy and Soil Science 2010, 56(2)183- 199.Doi: 10.1080/03650340902914024.
• G.Y.Jayasinghe, Y.Tokashiki, M.Kitou & K.Kinjo (2010). “Effect of synthetic soil aggregates as a soil amendment to enhance properties of problematic grey soil (“Jahgaru”) soils in Okinawa, Japan”. Journal of Communications in Soil Science and Plant Analysis 2010:41:649-664.Doi:10.1080/00103620903533959.
• G.Y.Jayasinghe & Y.Tokashiki (2010) “Evaluation of the use of synthetic red soil aggregates (SRA) and zeolite as substrate for ornamental plant production” Journal of Plant Nutrition 2010:33(14) 2120- 2134.Doi:10.1080/01904167.2010.519085.
• G.Y.Jayasinghe, Y.Tokashiki, I.D.Liyana Arachchi & M.Arakaki (2010) “Sewage sludge sugarcane trash based compost and synthetic aggregates as peat substitutes in containerized media for crop production”. Journal of Hazardous Materials. (174), 700-706 DOI: 10.1016 /j.jhazmat. 2009. 09.107.
• G.Y.Jayasinghe, Y.Tokashiki & I.D.Liyana Arachchi (2010) “Evaluation of containerized media developed by cattle manure compost and synthetic aggregates for ornamental plant production as a peat alternative”. Journal of Resource Recycling and Conservation 2010:54(12)1412-1418.
• Fajiri Anugroho, Makoto Kitou, Fuji Nagumo, Kazutoshi Kinjo & Jayasinghe G.Y. (2010).Potential growth of hairy vetch as a winter legume cover crop in subtropical soil conditions. Soil Science and Plant Nutrition 2010:56(02) 245- 262.Doi:10.1111/j.1747-0765.2010.00445.x.
• G.Y.Jayasinghe, Y.Tokashiki & I.D.Liyana Arachchi (2011). “Development of sewage sludge based synthetic aggregates for containerized ornamentals”. Journal of Environmental Technology (Accepted on 22.October 2010 and in press).
• G.Y.Jayasinghe & Y.Tokashiki (2011) “Influence of coal fly ash pellet aggregates on the growth and nutrient composition of Brassica campestris and physicochemical properties of grey soils in Okinawa, Japan.” Journal of Plant Nutrition (Accepted on 26th August 2010 and in Press).
• G.Y.Jayasinghe (2011) “Synthetic soil aggregates as a potting media for ornamental plant production” Submitted to the Journal of Plant nutrition (Accepted on 20 June 2011 and in press).
• G.Y.Jayasinghe & Y.Tokashiki (2010).”Synthetic aggregates produced by different wastes as a soil ameliorant, a potting media component and a waste management option in the book of “Waste Management Book” has been Published by INTECH Publishers (ISBN978-953- 7619-1X-1X.) Vienna, Austria.
• G.Y.Jayasinghe(2011) “Utilization of municipal solid waste compost in agriculture” in the book of “Waste management Book ”has been accepted by INTECH Publishers (ISBN 978-953-307-447-4).

• A paper titled “Influence of coal fly ash-based pellet aggregates addition on physicochemical properties of acid soil s in subtropical Okinawa, Japan and their effect on the growth and nutrient content of Brassica campestris” has been presented at the Japanese Society of Soil Science and Plant Nutrition on 15-18 September, 2009, Kyoto, Japan. G.Y.Jayasinghe, Y.Tokashiki & M.Kitou.
• A paper titled “Synthetic coal fly ash-paper waste aggregates as an option for waste management and a soil amendment to improve low productive soils” has been Presented for a presentation at the International conference in Asian Institute of Technology, Bangkok, Thailand on 5-7, January, 2009. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “Utilization of bagasses sewage sludge based compost as a peat substitution for Lettuce cultivation” has been presented for presented at the International conference conducted by the Soil Science Society of America (SSSA). 1-5, November, 2009, Petersburg, PA, USA. G.Y.Jayasinghe & Y.Tokashiki.
• A paper A paper titled “Substitution of peat for synthetic aggregates and bagassessewage sludge based compost as a containerized media for crop production” has been presented at the R’09 Twin World Congress, Nagoya, Japan 14-16, September, 2009 under the theme of “Promotion of innovative technologies and frameworks for resource management to improve material and energy efficiencies in the production, use and recycling of materials..” G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “ Exploitation of coal fly ash based synthetic aggregates as a granular fertilizer medium and a soil amendment to improve crop production in low productive red soil in Okinawa, Japan” has been presented at the international conference conducted by the Soil Science Society of America (SSSA). 5-9, October, 2008, Houston, Texas, USA. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “Synthetic red soil paper waste aggregates: as a potential soil amendment to enhance properties of problematic “Jahgaru” soils in Okinawa, Japan” has been presented at the conference conducted by the Japanese Society of Soil Science and Plant Nutrition, 8-12 September,2008,Nagoya,Japan. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “Assessment and Utilization of synthetic soil aggregates developed by using coal fly ash and paper waste” has been presented at the American Society of Soil Science, 4-8, December,2007, New Orleans, Louisiana, USA. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “Evaluation of the use of artificial zeolite and oil palm wastes as a substrate for crop production” has been presented at the Japanese Society of Soil Science and Plant nutrition, 20-24, August, 2007, Tokyo, Japan. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “Sustainable waste utilization to develop synthetic aggregates and their potential as a constituent of potting media.” has been presented at the International Pacific Congress at on 12-18, June, 2007, Okinawa, Japan. G.Y.Jayasinghe, Y.Tokashiki & M.Kitou.
• A poster titled “Study of the production, performance and the micro-morphology of synthetic light weight soil aggregates developed by using coal fly ash treated with starch as an organic binder” has been presented at the International Conference on Coal Science and Technology.9-14, October, 2005. Okinawa, Japan. G.Y.Jayasinghe, Y.Tokashiki & L.Vidhana Arachchi.
• A paper titled “Studies on improvement of rice straw biomethanation” has been presented at the international conference on Recovery, Recycling and Re-integration. 25- 29, Septemebr, 2005, Beijing, China. G.Y.Jayasinghe & L.Abegunawardana.
• A paper titled “Influence of mixing synthetic light weight aggregates developed by using coal fly ash and used paper as waste materials to amend the soils of `Kunigami Mahji`” has been presented at the conference conducted of Japanese Society of Soil Science and Plant nutrition . 6-9, September, 2005, Shimane,Japan. G.Y.Jayasinghe & Y.Tokashik.
• A paper titled “Development and exploitation of synthetic light weight soil aggregates produced by using `Kunigami Mahji` soils in Okinawa, Japan with coal fly ash and used paper”(In Japanese) has been presented at the conference conducted by Japanese Society of Soil Science and Plant nutrition (JSSPN). 6-9, September, 2005, Shimane, Japan. Y.Tokashiki & G.Y.Jayasinghe.
• A paper titled “Evaluation and utilization of synthetic soil aggregates developed by using different waste materials” has been presented at the conference conducted by Japanese Society of Soil Science and Plant Nutrition. (JSSPN).5-8, September, 2006. Akita, Japan. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled “Agricultural and horticultural utilization of fly ash aggregates” presented at the 3 rd clean coal seminar, 5-7, July 2006, Okinawa, Japan. G.Y.Jayasinghe & Y.Tokashiki.
• Presented a poster and stall in annul Industrial exhibition in Naha, Okinawa, 3-10, October, 2006. G.Y.Jayasinghe & Y.Tokashiki.
• A paper titled on “Anaerobic digestion of rice straw in batch-type biogas generators as an appropriate option to compensate rural energy and fertilizer needs of the paddy farmers while mitigating the methane emission from rice fields due to direct field application of straw.” Has been presented at 9th world congress in Antipen, Belgium 2001 September. KDN Weerasinghe, G.Y.Jayasinghe, LAY Dharshanie& W.Attanayaka.
• A paper titled “Fertility enhancement of rice fields through the application of anaerobic ally digested straw from batch type biogas generators, while mitigating the methane emission.”has been presented at the International conference on paddy soil fertility in Philippines (2000, April) K.D.N. Weerasinghe, G.Y.Jayasinghe & L.A.Y.Dharshanie.
• A paper titled “Biogas technology adoption to meet rural energy demand and organic fertilizer needs” has been presented at the International work shop in Sri Lanka on 1999 may on design performance and marketability of biogas systems. G.Y.Jayasinghe & K.D.N. Weerasinghe.
• A paper titled “Appropriate biogas generators for resource poor farmers in Sri Lanka to meet home energy and organic fertilizer needs” has been presented at the International Scientific conference on biogas science on 02-04, December,2009, in Erding, Germany. K.D.N.Weerasinghe, S.Wijetunge & G.Y.Jayasinghe.
• A thesis submitted in partial fulfillment to the BSc.in Agriculture on “Influence of straw and by-products of biogas generators as fertilizer materials on the growth and development of rice plant.” (In 1999 Jan) G.Y.Jayasinghe.
• A paper presented on “Influence of C: N and C: P ratios on rice straw biomethanation.” At Fifty eighth Annual session of Sri Lanka Association for the Advancement of Science: Pp 58 (2002, DEC) G.Y.Jayasinghe & K.D.N.Weerasinghe.
• A paper presented on “Assessment of the composition and the volume of biogas liberation from agricultural wastes.” at Proceedings of Eighth annual forestry congress held at coral gardens hotel Hikkaduwa, Sri Lanka Pp: 46(2002, Dec) G.Y.Jayasinghe & K.D.N.Weerasingh.
• A paper presented on “Manipulation of methane and biogas production of rice straw biomethanation” At Fifty ninth Annual session of Sri Lanka Association for the Advancement of Science : Pp 62 (2003,DEC) G.Y.Jayasinghe & K.D.N.Weerasinghe.
• A paper presented on “Anaerobic digestion of market garbage and paddy straw as an option to produce efficient biogas and fertilizer while acting as an environmental friendly technique to manage solid waste.” at Proceedings of ninth annual forestry congress to be held at coral gardens hotel Hikkaduwa, (2004, Jan.). G.Y.Jayasinghe & K.D.N.Weerasinghe.
• A paper presented on” Consequences of C: N and C: P adjustments of rice straw on biomethantion in an anaerobic digester” at First academic sessions of University of Ruhuna, Sri Lanka. (2003, July) G.Y.Jayasinghe & K.D.N.Weerasinghe.
• An Environmental Impact Assessment (EIA) Report Prepared to evaluate the consequences to the flora and fauna due to the proposed the Kakiri-obada reservior at Kakiri –obada, Walasmulla. G.Y.Jayasinghe & K.D.N.Weerasinghe.
• A paper Presented on “Design of a two-phase digester system to optimize biogasification of ice straw” at the Fourth academic sessions of University of Ruhuna,, Sri Lanka, 29th, January, 2007. S.Wijetunge, N.E.Punchihewa, K.D.N Weerasinghe & G.Y.Jayasinghe.
• A paper presented on “ Utilization of agricultural waste compost as an alternative potting media component with coir dust for leafy vegetable Ipomea acquatica. At 8th Academic Sessions conducted by University of Ruhuna on 22nd February, 2011. W.K.R.Thushara and G.Y.Jayasinghe.
• A paper presented on “synthetic Aggregates as a potting media for ornamental plant production at Sixty Sixth Annual session of Sri Lanka Association for the Advancement of Science 2010 DEC. G.Y.Jayasinghe.
• A paper presented on “Potential utilization of composted sewage sludge in growth media for lettuce cultivation at the International Symposium conducted by Faculty of Agriculture University of Ruhuna on 16th November 2010. G.Y.Jayasinghe and Y.Tokashiki.