Case Study #234
1. Headline: Pollution Prevention Assessment for a
Manufacturer of Starting, Lighting, and Ignition (SLI)
Batteries
2. Background:
What is EP3?
The amount of pollutants and waste generated by industrial
facilities has become an increasingly costly problem for
manufacturers and a significant stress on the
environment. Companies, therefore, are looking for ways to
reduce pollution at the source as a way of avoiding costly
treatment and reducing environmental liability and
compliance costs.
The United States Agency for International Development
(USAID) is sponsoring the Environmental Pollution
Prevention Project (EP3) to establish sustainable programs
in developing countries, transfer urban and industrial
pollution prevention expertise and information, and
support efforts to improve environmental quality. These
objectives are achieved through technical assistance to
industry and urban institutions, development and delivery
of training and outreach programs, and operation of an
information clearinghouse.
EP3's Assessment Process
EP3 pollution prevention diagnostic assessments consist of
three phases: pre-assessment, assessment, and post-
assessment. During pre-assessment, EP3 in-country
representatives determine a facility's suitability for a
pollution prevention assessment, sign memoranda of
agreement with each facility selected, and collect
preliminary data. During assessment, a team comprised of
US and in-country experts in both pollution prevention and
the facility's industrial processes gathers more detailed
information on the sources of pollution, reducing this
pollution. Finally, the team prepares a report for the
facility's management detailing its findings and
recommendations (including cost savings, implementation
costs, and payback times). During post-assessment, the EP3
in-country representative works with the facility to
implement the actions recommended in the report.
Facility Background
This facility manufactures starting, lighting, and
ignition (SLI) batteries. Most of the facility's output is
sold domestically, although about 20% is exported. The
facility operates one, two, or three 8-hour shifts
(depending upon the equipment, process, and season) and
employs 220 people. In 1993, they sold 231,000 batteries.
This assessment evaluated a facility that manufactures
lead-acid batteries used in automobiles and trucks. The
objective of the assessment was to identify actions that
would: (1) reduce the quantity of toxics, raw materials,
and energy used in the manufacturing process, thereby
reducing pollution and worker exposure, (2) demonstrate
the environmental and economic value of pollution
prevention methods to the battery industry, and (3)
improve operating efficiency and product quality.
The assessment was performed by an EP3 team comprised of
an expert in battery production and a pollution prevention
specialist.
3. Cleaner Production Principle: The assessment identified
various cleaner production applications including: process
modification, good housekeeping, new technology,
recycling, and material substitution.
4. Description of Cleaner Production Application:
Overall, the assessment identified nineteen pollution
prevention opportunities that could save over $1,521,206
(US) in the first 12 months for an investment of $522,500
(US). If implemented, these changes could reduce employee
exposure to lead dust, reduce energy and water use per
unit output, reduce the amount of lead purchased, reduce
lead-contaminated waste water, and improve product
quality.
Manufacturing Process
Facility operations can be divided into six main steps:
(1) conversion of scrap lead into cast panels, (2)
conversion of virgin lead into lead oxide powder and
paste, (3) pasting and curing of panels, (4) container
formation of batteries, (5) tank formation of batteries,
and (6) laboratory analysis and process controls. The
battery making process begins on two parallel tracks: the
facility recovers lead from used batteries that are
collected and brought to the facility, scrap lead is
recycled and then cast into grids, and virgin lead is
mechanically converted into a powdery lead oxide, which is
used to make a paste. These separate feeds merge at the
grid pasting machine where the paste is pressed into the
grids. Pasted plates are cured and then take one of two
paths to become battery elements: tank formation or
container formation. These processes convert the paste
into active material that will electrically charge and
discharge throughout the useful life of the battery. In
tank formation, this process takes place in large tanks
whereas in container formation, the cured plates are
assembled and formed in the battery case itself.
To make the lead oxide paste, lead oxide powder is mixed
with de-ionized water, sulfuric acid, and organic
expanders. One recipe makes a positive plate, while a
slightly different recipe makes a negative plate. The
pasted plates then move on a conveyor belt through a
drying oven. After pasting and drying, the plates move
into a curing chamber for about 48 hours to convert the
remaining lead into lead oxide.
In tank formation, the positive and negative plates are
immersed in tanks of low specific gravity sulfuric acid,
where electrodes pass a current through the plates. In the
positive plates, the current converts lead sulfate from
the paste into lead oxide. In the negative plates, the
reaction converts the paste into sponge lead, a very
porous, high surface area form of elemental lead.
Container formation employs the same electrochemical
process, but occurs in the plastic battery case instead of
the tank. Cured plates that are not tank formed must be
cut in half and assembled into battery elements, which are
then placed into batteries for container formation.
After tank formation, the plates go through a washing an
drying process to remove any remaining sulfuric acid.
Overall, the plate washing process accounts for over 60
percent of the factory's water contaminated with lead and
sulfuric acid.
Existing Pollution Problems
At the time of the assessment, there were a number of
pollution problems at the facility, including:
(1) waste acid from the used batteries that are cracked to
recover lead is disposed of on-site, (2) uncovered lead
slag and dust piles, (3) excessive energy used in smelting
ovens, curing rooms, and the tank formation process, and
(4) excessive wastewater generation in the grid pasting
and washing processes. In addition, over 2,500 kilograms
of lead oxide paste was spilled and fed into the smelting
process each day, using virgin lead where scrap lead would
suffice. Finally, several technological problems (e.g.,
the outdated lead oxide mill and lack of a moisture
analysis oven) increased raw materials use and adversely
affected battery quality.
Pollution Prevention Opportunities
Overall, this assessment identified nineteen pollution
prevention opportunities that could address the problems
identified and produce significant economic benefits for
the facility. If implemented, these opportunities could
save over $1,531,206 (US) in the first 12 months for an
investment of $ 522,500 (US).
The pollution prevention strategy is premised on the
belief that addressing sources of waste and pollutants
also improves the company's economic health by reducing
operating costs and improving product quality. In this
case, product quality is increased by (1) increasing the
lead oxide particle size by buying a liquid atomization
mill, (2) increasing the moisture content of the paste
recipes, (3) increasing the curing temperature, humidity,
and air circulation, (4) analyzing the moisture content of
the pasted plates on-site, at the oven, (5) monitoring the
smelting oven temperature and adjusting to the optimal
level, (6) curing larger batches of pasted plates, and (7)
utilizing cadmium sticks in the laboratory to measure cell
voltage.
The following is a lists of the opportunities for
pollution prevention recommended for the facility and
presents the environmental and product quality benefits,
implementation cost, savings, and payback time for each.
Because the quantities of pollution generated by the
facility and possible pollution prevention levels depend
on the production level of the facility, all values should
be considered in that context.
--Conversion of Scrap lead into Cast Panels--Smelting--
Options included
1. Cover slag and dust piles and clean
smelting room reduces worker exposure to lead
and lead dust. Costs $500 (US) provides
financial benefit of $3,750 (US) per year and
has a pay back period of less than two months.
2. Buy temperature monitoring instrument
to adjust oven reduces toxic emissions and slag
and reduces energy costs. Costs $1000 (US)
provides a financial benefit of $1000 (US) per
year and has a pay back period of one year.
--Casting Panels--Option included: Purchase improved
design mold which reduces waste, lowers energy use and
eliminates steps in the process. The cost is $100,000
(US). Financial benefit and payback period is
incorporated in plate cutting.
--Conversion of Virgin lead into lead oxide powder and
paste-- Options included:
1. Shovel spilled lead cylinders back
into the mechanical mill rather than smelting
ovens- conserve lead and energy. There is no
cost and the financial benefits equal $88,646
(US) per year therefore providing an immediate
payback.
2. Purchase a liquid lead automization
mill - improves efficiency and reduces emissions
of lead oxide powder. The cost is $200,000 (US)
which provides quality improvements.
3. Sell old equipment once the liquid
atomization mill is operating which recovers
some of the costs of new purchase. There is a
financial benefit of $10,000 (US) per year.
--Pasting and curing panels: Pasting-- The options
included:
1. Shovel spilled paste back into paste
hopper rather than smelting oven - which reduce
lead purchases, reduces volume of waste water,
and saves energy. There is no cost, it saves
$479,546 (US) per year with an immediate
payback.
2. Increase moisture content of the paste
- reduces scrap and extends battery life.
Improves the quality.
3. Reduce the water flow to the finishing
roller on paste machine - reduces water use and
volume of waste water. It save $2,000 (US)
year.
4. Buy a moisture analysis oven to make
better lead and to save energy. The cost is
$2,000 (US) it will provide and annual benefit
of $500 (US) per year therefor paying for itself
in two years.
--Pasting and curing Panels: Curing-- The options
identified included:
1. Install racks to cure larger batches
to save energy and extends battery life. The
$1000 cost will improve product quality.
2. Install mist sprayers, a heater, and
two fans in each cutting room improves battery
life, and therefore improves product quality.
3. Analyze the free lead content after
twelve hours of curing saves energy and extends
battery life. The financial benefits will
depend on the curing.
--Pasting and curing Panels: Cutting-- The options
identified included:
1. Eliminate the cutting process which
reduces scrap and saves lead and energy. The
cost is $100,000 with a financial benefit of
$70,956 per year and a payback period therefor
of less than 18 months.
2. Recycle drops to strap casting pot
rather than smelting oven - saves lead and
energy. The payback period is immediate as
there is no cost and financial benefits are
$20,520 (US) per year.
--Container formation: Immediately apply charge after
filling improves battery performance - there is no cost
and the payback is immediate of $36,288 per year.
--Tank formation of plates: Eliminate the process --saves
water and natural gas, reduces worker exposure to acid and
lead dust, reduces volume of waste water and improves
battery quality. The cost is $100,000 with a financial
benefit of $693,000 per year and therefore a payback
period of less than three months.
--Tank formation: Washing and drying of plates--Stop
washing all plates immediately will reduce waste water.
There is no cost and it will result in saving of $125,000
per year.
--Laboratory Analysis and Process Control: Laboratory
Analysis--Accurately measure individual battery cell
voltage assures battery quality. The cast of $500 (US)
will improve battery quality.
The total costs of these actions is $522,500 (US) and the total
financial benefits are $1,531,206 per year.
Evaluating Performance
EP3 is developing a methodology for measuring and tracking
pollution prevention performance. The approach uses simple but
critical ratios to compare data among facilities in the same
industrial sector.
This assessment identified four critical ratios, as shown in
Table 1 (below). The Assessment Team developed best industrial
performance (BIP) values for these ratios, and found that each
of this facility's current values were significantly above the
BIP values. The facility should be able to reduce its ratios
and come closer to the BIPs by implementing the pollution
prevention options listed above.
Ratio BIP
Current Ratio at
Facility
Kilograms of virgin 8.0 11.2
lead per battery unit
Kilograms of lead- 5.0 9.7
alloy feed per
battery unit
Liters of water used 50 150
per battery unit
Kilowatt-hours (kwh) 7 kwh 10.7 kwh
and cubic meters and and
(m3) of natural gas 5 m3 6.6 m3
per battery unit
Implementation Status
The facility has already implemented many of the low/no cost
recommendations, including covering recycled lead piles,
recycling dropped virgin lead into the lead oxide mill rather
than into the smelter, recycling waste paste into the hopper
rather than sending it to the smelter, and maintaining optimal
temperature and humidity in the curing room. In addition, the
facility has begun to implement several capital intensive
changes. For example, it has placed an order for boost charging
equipment ($ 100,000 US) and requested price quotes for a
liquid lead atomization mill ($ 240,000 US).
5. Economics: See above.
6. Advantages: See above.
There is an additional opportunity to prevent pollution
and conserve raw materials in the battery recycling
process. Before cracking the battery case, workers could
pour the acid into a large plastic plating tank. The acid
could be recycled (possibly through ion exchange) and
returned to the production process, replacing purchases of
high concentration acid.
7. Constraints: No information provided.
8. Contact:
EP3 Clearinghouse (UNITED STATES)
TEL: 1 (703) 351-4004
FAX: 1 (703) 351 6166
Internet: apenderg@habaco.com
9. Keywords: battery, good housekeeping, recycling, material
substitution, new technology, process modification, EP3,
lead, acid, plate, cadmium, water saving, smelting, USAID
10. Reviewer's comments: This case study was carried out in a
developing country in which EP3 has an established
programme. It was submitted to UNEP IE and edited for the
ICPIC diskette in August 1995. It has not undergone a
formal technical review.