The Tactical Garbage to Energy Refinery (TGER) is a trailerable, skid-mounted device capable of converting waste products (paper, plastic, packaging and food waste) into electricity via a standard 60 kW diesel generator. Additionally, the sys­tem can utilize available local biomass as a feedstock. Waste materials are converted into bio-energetics which displaces the diesel fuel used to power the generator set. The system also co-produces excess thermal energy which can be further utilized via a “plug and play” heat exchanger to drive field sanitation, shower, laundry or cooling devices. With additional engineering, the TGER could include a small sub­system to recover water introduced with the wet waste and produce potable water to further reduce logistics overhead. The system requires a small “laundry packet” of enzymes, yeasts and industrial antibiotics to support the biocatalytic subsystem.

Feed materials (daily)-01 Aug 08
Garbage (gallons)	90 20% paper, 50% cardboard, 30% plastic
Garbage (lbs)	513
Food (gallons)	58
Diesel (gallons)	3

Energy content of feed

Heats of Total (lb) Component comustion (btu/lb) LHV Total energy (BTU) Total energy (kWhr) 2.9 Carbohydrates 7200 20871.65 6.11713 359.1 Paper/cardboard 8000 2872800 841.9695 77.0 Plastic-polyethylene terephthalate 10250 788737.5 231.1657 77.0 Pastic-polystyrene 17800 1369710 410.439 20.9 Diesel (DF2) 18397 385233.2 112.9054 Total 5437352 1593.597

Electrical energy production

Total (kWh) 267.5

Offboard (kWh) 221.2

Total thermal-to-electrical energy conversion efficiency (% of energy content of feed) 16.8%

Offboard energy conversion efficiency (% of thermal energy content of feed)

13.9%

Diesel fuel savings (gallons)

27

Energy delivery efficiency (% of electrical energy for offboard use)

82.7%

% Contribution to feed energy Diesel 7.08%

Biofuels 92.92%

The residuals from waste conversion are environmentally benign including simple ash, which can be added to improve soil for agriculture, and carbon dioxide.

The TGER will deploy on a XM 1048 5-ton trailer and is designed to sup­port a 550 man Force Provider Unit (FPU), which produces approximately 2,200 pounds of waste daily. On a daily operational basis, this would conserve approx­imately 100 gal of diesel. The capability for such conversion would provide immediate and responsive energy requirements for expeditionary operations as well as yielding estimated cost savings of $2,905/day [10]. A projected fielding plan for the TGER involves identification of current Modified Table of Organization and Equipment (MTO&E) trailers associated with FPU kitchen support which would then be modified to include the waste conversion technology. This would avoid any changes to the MTO&E or prime mover designation. Estimations indicate that the additional tasks associated with maintenance support for the operator and mechanic would not exceed those standards for the assigned Military Occupational Specialty and Generator Mechanic. Higher order support may follow a Contractor Logistics Support or low density support plan similar to that for the reverse osmosis purification unit equipment.

Anticipated field employment of the system is such that the TGER would be pulled by the assigned 5-ton family of medium tactical vehicles assigned to accom­pany the FPU Containerized Kitchen. Upon occupation of the FPU site, the TGER would start up initially on diesel fuel alone. This would provide immediate power to the kitchen and begin to heat up/power the system components. As waste is devel­oped from the kitchen, it will be introduced to the TGER and the two energetic materials (synthetic gas and ethanol) will begin to displace the diesel fuel. By six to twelve hours (depending on the waste stream), the TGER will run on 98% waste energetics and is capable of running for 12 h with a one hour maintenance shut-down intervening.

Improvements for future models revolve around three subsystems: the gasifier, bioreactor and materials handling. The current downdraft gasifier equipment is too complicated and unreliable under desert conditions. However, modifications to the current design could reduce the complexity of the system and, with a thorough inspection, repair and evaluation by the manufacturer, we believe a number of alter­ations to the downdraft gasifier would mitigate its reliability problems. Ultimately, it would be advantageous to consider alternative thermo-chemical approaches.

The issues with the bioreactor are much less complex and more easily addressed, as the system was custom built by Purdue University and several supporting subcontractors. Repairing and upgrading this system will primarily involve replac­ing and upgrading the two heat exchangers, modifying the system software to accommodate the changed thermo-dynamics and thermal management, and adjust­ing the “plumbing” of the ethanol collection and delivery system.

During the intervening 18 months since the TGER fabrication, the commercial field of biomass fuel processing has greatly expanded. There are a number of new options for third party equipment such as improved shredders, pelletizers and pellet drying systems which did not exist previously.

2 Conclusion

Throughout the course of the 15 month program the TGER underwent testing in a variety of conditions and environments. Performance characteristics of the TGER varied in each environment and provided valuable information as to how to improve

Diesel Ethanol Solid waste Liquid

consump- consump — Ethanol processing waste Total waste

Power Power tion tion production rate (pellet processing processing Diesel

output efficiency rate rate rate production) rate rate Savings

54 kW 90%	1 gph 1 gph	1 gph	60 lb/h	13 lb/h	1,752lb/day3.6 gph
Table 6	Power vs. Fuel Consumption Table Recorded at Purdue University
	Power Idle	25 kW	35 kW	45 kW	55 kW
Fuel Diesel	100%	1.3 gph	1.0 gph	1.2 gph	1.0 gph
Fuel gas	0 scmh	57 scmh	65 scmh	60 scmh	65 scmh
Ethanol	0 gph	0 gph	0 gph	0.5 gph	1 gph

Table 7 TGER performance data set recorded at VBC

Average TGER performance data at victory base camp

Solid waste processing

Power Diesel Pellet (pellet Liquid waste Total waste

efficiency consumption consumption production) processing processing Diesel saved

~80% 2 gal/h** 60 lb/h 54 lb/h 13 lb/h 1,752 lb/day 2.6lb/h the overall design of the TGER in order to achieve what we believe to be the optimal theoretical performance characteristics shown in Table 5.

Prior to the deployment to Victory Base Camp, the TGER underwent testing in a controlled environment at Purdue University. The fuel consumption of all three fuels (syngas, ethanol and diesel) was measured at varying loads using digital flow rate sensors as seen in Table 6.

Although the TGER did not perform as well in Iraq as it had when in a con­trolled environment at Purdue University, it did demonstrate the ability to conserve fuel and remediate waste in a forward deployed operational environment. Table 7 shows the TGER’s performance characteristics when it was running under optimal conditions at Victory Base Camp. With improved engineering and further devel­opment all of these performance characteristics can be improved, maximizing the TGER’s potential as a viable portable power generation system.

Acknowledgements The authors gratefully acknowledge the funding support of the US Army’s Rapid Equipping Force, the Small Business Technology Transfer Research program and the Research Development and Engineering Command. We also thank the many forward deployed personnel at Victory Base Camp, Iraq for their support on the ground. Special thanks to Ms. Donna

Hoffman for pre-deployment and deployment support and for extensive editing and preparation of the manuscript.