Energy Production Comparisons

Assumptions:

Essentially, in the case of municipal wastes, the cost of fuel is equal to the cost of collection and transportation of the wastes.

The lower energy conversion efficiency of municipal waste is due to higher moisture content compared to other fuels. This analysis considers that the production of one (1) Kwh using municipal waste will require 60% more energy, or 10,500 BTU/Kwh compared to 6,350 BTU/Kwh required using an average of other fuel.

In those countries that utilize oil for all or part of their energy requirements, the substitution of municipal waste would relieve oil for export or other uses and, thereby, generate higher return per unit of this energy source, compared to the use of the same oil, domestically, to produce electric power.

Energy source cost - C.I.F. Plant:

EQUIVALENT FUEL VALUES
(AS RECEIVED BASIS)

SOURCE: Environmental Protection Agency (USA)

ULTIMATE ANALYSIS OF MUNICIPAL SOLID WASTE COMPONENTS
(percent by weight)

SOURCE: Environmental Protection Agency (USA)

Conclusions:

This simple cost comparison indicates that, if the municipality imputes a charge for the real cost of collection and transportation of waste to the plant, the cost per BTU used for the conversion of the waste to one (1) kWh of electric power will be the lowest compared to other sources of energy and far cheaper than the use of oil.

At an imputed cost of USD 10.00 for each ton of municipal waste received, it will almost equalize the cost of energy created by burning oil. By comparison, the cost per BTU of using natural gas would be seven times higher and coal would be nine times higher than the cost of using municipal waste! 

 

Using oil (C.I.F. plant)	1.08 cents per Kwh
Using tires (C.I.F. plant)	1.59 cents per Kwh
Using natural gas (C.I.F. plant)	9.14 cents per Kwh
Using coal (C.I.F. plant)	1.53 cents per Kwh
Using municipal waste (C.I.F. plant)	.74 cents per Kwh

Cost of Electric Power produced

To consider the cost of electricity production, in detail, a broader analysis of each city's municipal solid waste capabilities has to be examined. Our plant design is based on the experience accumulated in countries around the world, and the analysis of the municipal waste information received from large municipalities, in particular. While the Kcal/Kg content of municipal waste varies considerably between cities, the experience obtained in urban and rural installations enables us to offer an unconditional assurance that we can achieve successful and profitable operations in any municipality - large or small.

Basically, our MSW units will burn solid waste of any composition. No pre-treatment of the garbage is required, therefore no additional costs are involved. The system raises the incinerator's temperature to 1,800 degrees F in a very short time. At that temperature, all combustible material (organic and inorganic)
and contaminated material, will be combusted without the need to add any other fuel at additional cost. In this regard, the computerized temperature controls ensure that our units offer a considerable cost advantage over all other thermal waste treatment plants on the market.

The short time interval that elapses from the reception of the garbage to its gasification allows a continuous recapture and combustion of particles and gases and the high retention of heat. This, in turn, minimizes the cost of gasification and, consequentially, reduces the cost of electricity generation.

The evaporation of all moisture contained in the garbage, followed by the condensation of the vapors within a closed system, minimizes the use of external water and the associated costs of water acquisition or disposal.

Continuous collection of ash, and its potential use in the production of building materials, creates a secondary source of revenue and eliminates another cost, thereby further reducing the cost of the electricity produced.

Energy Balance:

To compute the real costs of the municipal waste's treatments and the cost of the electricity produced, it is important to note that our MSW units burn solid waste of any composition. Nevertheless, as far as energy conversion efficiency is concerned, wastes (municipal or other) of less than 50% combustible components will reduce the amount of heat available, thereby lessening the economics of the energy conversion process, and its technical efficiency. Such a circumstance is extremely rare and we have yet to encounter a municipal waste stream that offers an insufficient level of combustible materials. In the event that waste with excessive moisture content is received, the plant design allows for the on-site storage of waste for up to three days to allow drainage into a closed water recycling system.

Here are two examples of waste streams: in a major urban center.

Sampled municipal waste composition (percentage)

	Rio de Janeiro Section #1 (Dry material)	Rio de Janeiro Section #2 (Wet material)
Paper () carton	22.25%	17.00%
Plastic	15.09%	4.70%
Textile	2.50%	5.00%
Metals	3.09%	4.90%
Glass	3.60%	10.50%
Carton	na	3.00%
Construction material	.97%	2.00%
Organic material	48.89%	40.00%
Leaves	2.46%	na
Wood	.53%	1.00%
Rubber	.18%	na
Hides	.16%	na
Bones	.33%	na
Other small aggregates	na	6.90%
Water	na	5.00%
Total	100.00%	100.00%
Combustible material	92.23%	77.60%

Na = no information available

For this analysis, we used the Rio de Janeiro example due to the size of the municipality and the fact that its waste stream offers similar characteristics with those of other large cities around the world.

According to the information above, the residential municipal waste in Rio de Janeiro, at 70% humidity, has an energy content equal to 1,500 Kcal/kg.

Obviously, calculating the energy content of the same waste at 20% humidity (after drying) will result in:

 

At 70% humidity:	1,500 Kcal/Kg = 5,948.59 BTU/Kg = 2,703 BTU/Lb
Equal to (approximately)
At 20% humidity	6,750 BTU/Lb!

Given the high level of water content, the production of 1.0Kwh of electric power by our MSW unit, using the waste composition as indicated, requires 16,390 BTU/Kwh compared to 10,500 BTU/Kwh required by conventional oil firing power plants. This considers the energy required for the drying process of the material to the 0% humidity level, and full energy conversion.

An average municipal waste generated energy content is at the lower value of solid waste's scale of 5,400 BTU/Lb (see previous section). As another example, consider the lesser value of Bucharest municipal waste energy content of 5,050 BTU/Lb.

For a daily production of electric power, by this plant of 5MW capacity, the balance of energy is as follows:

Energy demand = 5,000 Kwh * 24 hours * 16,390 BTU/kwh = 1,966,800,000 BTU

Energy supply = 250 MT waste * 2,200 lb/ton * 5,050 BTU/Lb = 2,777,500,000 BTU

This implies that, even at 80% conversion efficiency, the energy supply meets the energy demand for the full production of the 5MW capacity.

Expressed in specific terms, the incineration of municipal waste in Bucharest would provide the following results:

 

On the supply side:
	-	Average Bucharest garbage Kcal/Kg content = 1,500 Kcal/Kg
	-	1 Kcal/Kg         = 3.97 BTU/Kg
	-	1,500 Kcal/Kg = 4765 BTU/Kg, at 70% humidity (wet)
	-	1,500 Kcal/Kg = 2,165 BTU/Lb, at 70% humidity (wet)
		= 5,050 BTU/Lb, at 0% humidity (dry)
Equivalent units:
1 Kwh =		860 Kcal
=		1,595 gram vaporized at 100 degrees C
=		7.9 Kg water heating from 20 degrees C to 100 degrees C
		5,890 BTU = Total requirement of BTUs to evaporate 1.0 Lb of water at 20 degrees C
On the demand side:
	-	production of 1.0 Kwh requires the use of 10,500 BTU
	-	the reduction of garbage humidity from 70% humidity to 0% humidity will require 5,890 BTU/Lb which implies that:
	-	production of 1.0 Kwh require the total supply of 16, 390 BTU (or 16,390 BTU/Kwh)
Which implies:
	-	an existing surplus energy that can sustain additional generating capacity of .41MW (810,200,000/16,390/5000/24 = .41 MW), or 8% surplus
	-	at 80% efficiency conversion, the existing surplus of energy can sustain additional generating capacity of .13MW, or 2.6% surplus
	-	that the energy supply exceeds the energy demand for the full production of the 5MW capacity
	-	that the waste being disposed must only contain 1,500 Kcal/kg to supply the necessary energy at 250 TPD

Conclusion:

The energy balance shown here indicates that the Rio de Janeiro municipal waste energy content is more than sufficient to provide the energy required for the production of 5MW during the incineration of 250 tons of waste per day. The same would be true of the waste-to-energy potential of municipal waste in almost any other medium or large city.

The performance indicators of the system (MSW units) are detailed in the Independent Environmental Consulting company report, and the American EPA certification. 

Those performance indicators and norms are maintained, and confirmed to the American EPA standards and regulations, throughout the operating life-span of the unit..

If co-generation of electricity and steam by our units is required, then any plant that produces the necessary steam to operate a 5 MW turbo-generator, can use some of the steam for the power generation, and divert a portion of the steam for a heated-water delivery system. It should be clear that in this case the options are:

• Shut off the turbo-generator for a specific time period and alternate the supply of electricity or steam
• Permanent co-generation of steam and electricity. To do so, the buyer will have to define the required combination, and the size of a the turbo-generator will be adjusted to suit the available steam.
• If the heating water system is closed-loop, and the units can retain the water, then the heated-water distribution system will act as the cooling system to the plant, and only negligible power is lost. The unit will produce the same 5MW of electric power.

Notice to Reader: All installations are unique and subject to specific design and pricing.