Environmental risk of waste and its management - Environmental Deterioration and Contamination: Problems and their Management - page 152

emissions from waste management contribute to all of these, and when emissions
during the whole life of materials and products are included, the contribution of waste
management, including prevention, becomes significant.
Air quality is evaluated by considering acidification, ozone creation and depletion,
and toxicity. Acidification has direct and indirect damaging effects such as nutrients
being washed out of soils, increased solubility of metals into soils, and damage to
stone buildings. Photochemical ozone creation potential (also known as summer smog)
is implicated in impacts such as crop damage and increased incidence of asthma.
Waste management options can highly affect acidification through emissions from
energy use, emissions of nitrogen and sulfur oxides, and hydrocarbons contributing
summer smog.
Water quality impairment due to eutrophication means the addition of exces-
sive amounts of organic or inorganic fertilizer to land or water. Excessive growth
and consecutive death of plants and microorganisms such as algae and phototrophic
cyanobacteria can lead to decreased oxygen levels in water, creating conditions which
cannot support diverse life. Eutrophication may be caused, for example, by leachate
or effluent from waste disposal systems and from agricultural land being mixed and
diluted with large amounts of non-contaminated runoffs.
Resource depletion is an important element of LCA, meaning the decreased
availability of natural resources. These may be renewable (e.g., wood) or nonre-
newable (metals). As economies around the world grow, demand and competition
for finite resources—including raw materials and fuel—also increases. Many of these
resources could potentially be reduced to unacceptable levels. This will have a range
of environmental and economic impacts.
Alternative options within the waste hierarchy can reduce our demand for
resources and extend the life of resources. Their selection from the available options
can be based on the results of LCA.
Evaluation of waste management options by LCA should take into account
the whole life cycle of waste treatment comprising collection, preparation for
use and treatment, material and energy requirement of all these steps as well
as residues and emissions from each step of the treatment. The type and qual-
ity of the product of waste treatment compared with the substituted product as
well as local circumstances such as transportation (distance, accessible means of
delivery, etc.) are also decisive parameters in LCA. Comparative evaluation of
the most feasible alternatives includes recording the alternative scenarios, evalu-
ating environmental impacts, evaluating the beneficial products, and analysis of
uncertainties.
As an example, a Hungarian case study on the alternatives of sewage sludge treat-
ment shall be introduced. The local alternatives of the previously practiced sewage
sludge disposal without methane collection and its beneficial products are listed
below:

- Methane production from disposed waste: 140 kWh/tonne electricity;
- Composting and use for nutrient supply on soil: 14 kg N/tonne, 3.4 kg P/tonne,
and 3.5 kg K/tonne;

- Incineration of the sludge in the cement works for heat production instead of fossil

energy sources: 13.5 MJ/tonne = 3.75 kWh/tonne heat energy.