Nicholas P. Cheremisinoff. Handbook of Solid Waste Management and Waste Minimization Technologies

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than not to occur. As example; if landfilling is relied upon to dispose of

hazardous wastes, the potential exists for the liner to be breached and

contaminate the groundwater, resulting in offsite and third-party damages. Or if a

manufacturing operation relies on a chemical component that is toxic, workers

could sue a company for chromic exposures resulting from their handling of the

material over their years of service. This in turn could result in an insurance

company raising premiums for medical coverage. If these types of scenarios are

more likely to occur than not, or simply stated, have a reasonably high

probability of occurrence, then there is a strong basis for choosing pollution

prevention and waste minimization strategies.

Tier 3

Future and Long-Term Liability Costs

Medical claims from

personal injury and

chronic health risks for

workers

Off-site damages and

remediation

More stringent

compliance

Toxic tort

On-site remedial

action costs

Inflation

Property devaluation and

restricted resale

Litigation fees

Class action suits from third-party damages

Figure 4. Examples of costs related to future events (i.e., long-term and

future liabilities).

Negative consumer

response

products

boycotted

Mergers, acquisitions,

joint ventures halted

because

high risks

from poor

environmental

Property transaction

laws block

restrict

asset sales

due to

environmental

damages

Insurance companies

raise premiums

drop

coverage because

high risks from poor

environmental

performance

and

liabilities

Tier

Less Tangible Costs

Negative investor

confidence

stock

prices fall

Lend-lease laws

impede property sales

and/or impose costly

and long-term cleanup

actions

Lending institutions

refuse

extend

offer favorable lines

credit

Becoming

the

target

for frequent

inspections

and

scrupulous

enforcement

regulators

Impacts from poor supply chain;

environmental risks

Figure 5. Less tangible costs from poor environmental management practices

that are hard to predict.

Less tangible costs (tier 4) are even more difficult to grasp, but they do play a

critical role in developing the proper investments for environmental management

strategies. Fig. 5 provides some examples. These again are cost impacts that can

arise from poor environmental performance. But again, the poor performance

may come from control-based strategies that consistently meet compliance

schedules, such as site cleanup costs at the time operations are shut down or are

sold. The main point is that if operations never generated waste or pollution, then

the possibility of ever having to deal with the financial impacts arising from their

generation and existence would never have to be addressed.

Further to tier 4 considerations, there is an ancient Chinese proverb that says that

10,000 years of an impeccable reputation can be destroyed by a single event. A

single major environmental mishap can shake investor confidence, cause

consumers to boycott products and seek out alternatives, and prevent joint

ventures, mergers; and acquisitions from moving forward because of the concern

for inheriting some of the financial liabilities associated with an environmental

exposure issue. Lending institutions since the 1980s have consistently turned

down loans and limited lines of credit to companies that have the perception of

poor environmental performance. Many states have property transaction laws that

require environmental audits as a prerequisite to property sales. When wastes and

pollution persist, even though they have been controlled to within legal limits of

discharge, residual levels or stockpiled wastes can become issues under these

laws and impose restrictions or terms for cleanup before a transaction can

proceed. An even more complex consideration is a company's relationship with

subcontractors and suppliers. For large multinational corporations, public image

and investor confidence are major concerns. When suppliers show poor

environmental performance or are implicated in a serious environmental mishap,

the perception is simply guilt by association. This is an area known as supply

chain environmental risk management (SCERM). This is however, a subject area

that goes beyond the focus of this volume.

P2 AND WASTE MINIMIZATION AT WORK

The following case study, summarized from EPA-625-7-91-017, illustrates how

P2/waste minimization is applied in practice to identifying alternative strategies

for solid waste management.

A small pharmaceutical plant manufactures erythromycin base and erythromycin

derivatives (erythromycin thiocyanate, erythromycin stearate, erythromycin

estolate). These products are used as growth promoters and as a disease

preventative in animal feed. The products are manufactured as bulk chemicals for

further processing.

To identify alternative strategies based upon prevention and waste minimization,

an assessment by a team of company personnel was applied. At the time of the

assessment the plant was operating at 50% of its design capacity. The

manufacturing technology is based on batch fermentation.

Note that an assessment or audit has several stages to it. In a later chapter we

will summarize the various steps to conducting waste minimization and pollution

prevention audits. Audits are both qualitative and quantitative in nature. It is the

application of material and energy balances that plays a major role in identifying

cost savings opportunities and assisting in the stimulation of ideas for replacing

end-of-pipe treatment technologies with preventive practices.

Figure 6. Process flow scheme for pharmaceutical plant example.

In reading over the following case study, bear in mind that the operations of any

plant are dynamic, and audits provide only a brief snapshot of the events

occurring. For this reason, effective waste minimization and pollution prevention

Inoculum organisms

and nutrients

SEED

TANK

Vent to

Atmosphere

Filter Precoat

and Water

FERMENTOR

Nutrients

ROTARY

VACUUM

FILTER

Air

Filtered

Solids to

Disposal

Liquid

Precoat

to Sewer

CRYSTALLIZER

UNIT

CENTRIFUGE

Spent

Solvent to

Recovery

Spent

Solvents

Recovery

Raffinate

SOLVENT

EXTRACTION

Vent to

Atmosphere

DRYER

Product to

Warehouse

audits need to incorporate follow-up sessions, with a focus on monitoring the

improvements over time.

The raw materials used in the manufacture of products are:

• Inoculum organisms

• Nutrients for fermentation (e.g., sugar, flour, fillers)

• Solvents for product recovery (acetone is used for product recovery during

erythromycin base campaigns, and amyl acetate is used for base derivative

manufacturing campaigns)

o Ammonium thiocyanate (for the manufacture of erythromycin thiocyanate)

• Acetic acid for processing

• Diatomaceous earth filter aid for fermentation broth processing

• Sodium carbonate, sulfuric acid, and sodium hydroxide for pH control

The Process

Fig. 6 illustrates a simplified process flow sheet of the operation. Following the

process flow scheme, the steps to manufacturing are as follows:

A lab culture of inoculum is delivered to a sterile 2000-gallon seed tank

containing nutrients suspended in an aqueous medium.

After the initial fermentation period the seed tank contents are transferred to

a 67000-gallon fermentation vessel. The entire fermentation cycle is 7 days,

with nutrients added over the course of the fermentation. During this

process step, the contents of the vessel are aerated and mildly agitated. The

contents are carefully monitored for sterility. Fermentation off-gas is

released to the atmosphere.

Upon maturation the harvest solution containing erythromycin base is

transferred to a holding tank for further processing. Approximately 5

batches per week are harvested. Once the plant goes to full capacity,

harvesting will increase to 10 batches per week.

The erythromycin base is next separated from the fermentation broth by

means of rotary vacuum filtration. The filtration units are first precoated

with an aqueous slurry of filter aid. The aqueous filtrate from the filter aid

application step is discharged to the sewer. Solid cake is scraped from the

filter surface using a doctor blade. The cake drops onto a conveyor belt,

and from there it is transferred to a disposal bin for off-site disposal.

Filtrate containing the erythromycin base is sent to the solvent extraction

stage of the process.

The product-recovery phase is based on solvent extraction. The

erythromycin is recovered using multistage liquid-liquid extraction. Rich

organic solvent layer and the raffinate (the water layer that contains some

solvent) are recycled.

6. The erythromycin-rich extract is sent to a crystallizer for product recovery.

In the next step, crystallized erythromycin base is separated by

centrifugation. The centrifuge cake is sent to a fluid bed dryer, and the

centrate (spent solvents) are recovered and recycled.

8. The dried, recovered product is drummed in the last stage of the process

and is ready for shipment to customers.

9. For the production of erythromycin thiocyanate, erythromycin base is

reacted with ammonium thiocyanate prior to crystallization. It is then

crystallized, centrifuged, dried, and drummed.

The Waste Streams

The following are the waste streams generated during manufacturing.

Filtration Process Wastes

The harvests are filtered using rotary vacuum filters coated with diatomaceous

earth filter aid. The wastes are the aqueous precoat filter plus the wet filter cake.

During the operation, the precoat is applied continuously at a rate of 1100 kg/hr.

The filtrate is discharged to the sewer without any pretreatment. Solid filter cake

waste (mycelia and filter aid) are generated at a rate of 1243 kg/hr. This waste is

removed to an off-site landfill in 5- to 10-ton load shipments. All of the waste is

considered to be nonhazardous. The solid filter cake waste is the largest waste

stream generated by the process on a volume basis. The unit costs for disposal

are as follows. A waste hauler has been contracted at a rate of $160 for the first 6

tons,

and then $16 per ton thereafter. The plant disposes between 7 and 10 loads

per week.

Solvents

Spent solvents are recycled from the product recovery and purification stages of

the process. Between 2000 and 3000 gallons of solvent is used for a single

fermentation harvest. The solvent recovery stage of the operation generates about

two 55-gallon drums of still bottoms per week, which is a regulated hazardous

waste.

Equipment Cleaning Wastes

The process equipment must be thoroughly cleaned and sterilized between

manufacturing campaigns in order to ensure product purity and to maintain

operating efficiency. These washwaters are generated intermittently. A caustic

solution is used to clean out the fermentation vessels, and the washwaters are sent

to the sewer. The amount of washwaters generated in this operation is not

measured.

Spills

Spills result from inadvertent material discharges. Two types of spills were noted

during a walkthrough of this facility. These are spillage of dry filter aid material

and wet filter cake. Spills are an obvious housekeeping issue at any plant

operation. Most often they are not tracked and so the cumulative losses,

including financial, are rarely realized. A spill prevention program is a well

worthwhile activity and one that is a low-cost P2 investment. Monitoring the

savings can provide the incentives for implementing more P2 and waste

minimization activities.

Air Emissions

Air emissions from the process predominantly occur from the solvent recovery

and the product-drying stages of the operation; however, there are fugitive air

emissions occurring at various points in the downstream product finishing stages.

Air emissions problems from a process like this can represent a formidable

challenge in terms of control and permitting. In this example we only focus on

the solid wastes.

Waste Minimization Practices

The following are recommended actions for reducing the wastes generated.

Filtration Process Wastes

The liquid waste generated by the vacuum filters is nonhazardous, and there are

no real costs associated with sending this material for final disposal to the sewer.

Hence, no corrective actions on the part of the company are needed, and there

are no cost advantages to considering other strategies.

The filter cake is a nonhazardous and nonregulated waste, but it does cost the

company to manage and dispose of this material. There are 10 loads per week of

this material that are transported to an offsite landfill. This translates into 364 to

520 loads per year (or about 3,276 to 4,680 tons per year) of filter cake waste to

the landfill. Furthermore, this waste quantity will increase significantly once the

plant reaches full capacity.

At a cost of $208 per 9-ton load, the current yearly costs for filter cake waste

disposal is between $76,000 and $108,000. At the plant's full operating capacity

the disposal costs will increase to $250,000 per year. Clearly there are very

attractive savings from eliminating or reducing this waste. In fact, there are from

$400,000 to possibly more than $1 million over a 5-year period associated with

the disposal of this waste stream. This is money that could be used for

modernizing the plant, increasing capacity and addressing debottlenecking issues,

enhancing product quality, or even investing in short-term certificates of deposit.

Instead of paying this money to a waste disposal contractor, the following

alternatives might offset some or all of these costs:

Alternative 1: Sell the spent filter cake material as a fertilizer. In order for this

material to be marketable as a fertilizer the nitrogen, phosphorus, and potassium

(N + P + K) levels must be above 5%.

Alternative 2: The waste has the potential to be sold into a market that has a need

for soil fillers and conditioners. These markets are often regional, and so some

effort is needed in identifying a potential customer. In addition, the waste has an

odor problem, which would make it unacceptable in some applications. To

eliminate the odor problem, the waste would likely require some posttreatment

step.

This would be an offset cost that needs to be carefully assessed in

evaluating this proposed option.

Alternative 3: The third alternative is to replace the rotary vacuum filters with an

alternative technology that does not create as much solid waste. A possibility is to

use ultrafiltration, which would eliminate the need for a precoat filter. This

approach would achieve the desired volume reduction needed to bring down the

costs for disposal. It does require a proof-of-principle demonstration through

pilot and perhaps plant trials, but with up to $1 million over a 5-year period at

stake, the strategy is well worth defining.

Solvents

The current solvent-recovery process includes a stripping column, an evaporator,

and a rectifying column. In the solvent-recovery stage about 99% of the solvents

are recovered and recycled through the process.

The solvent requirement per harvest is between 2000 and 3000 gallons, and the

cost of raw solvent is $1.78 per gallon. Hence, recycling saves between $3530

and $5290 per harvest. These savings are offset by:

• the operating costs for the recovery units

• still bottoms disposal (two 55-gallon drums per week still bottoms are

generated. These wastes must be incinerated and cost the company between

$250 and $300 per drum)

• solvent make-up for the nonrecovered solvent

Although there are some small credits associated with the inefficiency of

recovery, at 99% recycling this represents a low priority for the plant. If

feedstock prices for solvents increase in the future, a level of effort would be

justified in improving the recovery efficiency.

Equipment Cleaning Wastes

Since the washwaters are nonhazardous and do not require any pretreatment prior

to being disposed of to the sewer, there are no credits to try and capture by

eliminating or minimizing this practice.

Spills

The only spills observed are those involving the filter cake handling. There are

small savings associated with losses of diatomaceous earth and hence some

improved P2 housekeeping practices should be applied to minimize these losses.

For the spent filter cake spills, there can be financial losses associated with these

losses should we find this waste to be applicable as a byproduct stream (i.e., as a

fertilizer or soil additive). Again, low-cost measures such as improved P2

housekeeping should be practiced to minimize such incidents to avoid possible

safety hazards among workers, if for nothing else.

Synopsis

This is an example of the kinds of thought processes that go into a P2 and waste

minimization assessment. The assessment consists of an audit of the operations

the focus of the audit is to do the following:

Identify the environmental aspects associated with each unit operation

within the process.

Assess the impact from the environmental aspect on the business operations,

in terms of both compliance and costs.

Devise more cost-effective options that achieve compliance.

In this case study, there are no serious hazardous wastes handled in the

operation, except for the still bottoms, and occasional caustic wash waters, which

could not be quantified in the analysis. The potential costs savings associated

with managing the solid waste are direct, and there are sizable and well-defined

credits to try and capture by minimizing or eliminating the waste stream

altogether. An alternative technology investment (the microscreens) can reduce

the volume of solid wastes. This clearly is attractive from the standpoint of

improved environmental performance. Whether the investment is attractive

enough or can be justified by a reasonable payback period would have to be

determined from a LCC analysis.

A SHORT REVIEW

There is an overwhelming number of success stories that illustrate the benefits of

pollution prevention strategies. Many examples for a variety of industry

categories are summarized in earlier publications devoted to this subject

(Cheremisinoff, N. P., Handbook of Pollution Prevention Practices, 2001, and

Cheremisinoff, N. P. and A. Bendavid-Val, Green Profits: The Manager's

Handbook for ISO 14001 and Pollution Prevention, 2001). These case studies

show distinct financial advantages to companies by identifying reductions not only

in pollution and the costs associated with pollution/waste management, but

through reduced raw material consumption, energy savings, reductions in

treatment and disposal of wastes, and reductions in labor associated with

environmental management. Many P2 and waste minimization strategies, such as

substituting toxic materials with safer alternatives, do not require process

changes, and as such are simple and cost very little to implement. The areas in

which P2 have proven effective include the elimination and reduction of impacts

from:

• Treatment, disposal, and associated labor costs

• Wildlife and habitat damage

• Property devaluation

• Remediation costs

• Civil and criminal fines

• Permitting fees

• Insurance costs

• Process outages and disruptions

There are case studies that testify to the fact that P2 benefits result in:

• Enhanced public image - consumers more favorably view businesses that

adopt and practice P2 strategies, and the marketing of these practices can

assist in increasing a company's profits.

• Increased productivity and efficiency - P2 assessments have proven helpful in

identifying opportunities that decrease raw materials use, eliminate

unnecessary operations, increase throughput, reduce off-spec product