Civilisation’s bi-products

ENVIRONMENT

By GODFRIED ANGI
MY next topic of discussions will focus on wastes; their sources, generation, collection, storage, transportation and disposal.
Wastes are substances that are by-products of material substances after use and are no longer required for any further use. In other words, wastes are unwanted or unusable materials. They are any substances discarded after primary use, or is worthless, defective and of no further use.
Some wastes by-products are not necessarily wastes when they can be further used for any other purpose and or recycled. Aluminum cans and empty plastic bottles can be re-processed and be re-used or they can be re-used as water containers.
Source and types of waste
The sources of wastes include industrial wastes, commercial wastes, domestic wastes, agricultural wastes. These wastes can be biodegradable wastes and non-biodegradable wastes. Other types of wastes include agricultural waste, animal by-products, biodegradable wastes, biomedical wastes, bulky wastes, business waste and the list goes on.
There are five main types of wastes; liquid wastes –found in the households and industries; organic waste is common household wastes; recyclable rubbish and hazardous wastes. There are three main category of wastes; hazardous waste; toxic chemical wastes and municipal solid wastes.
Wastes are produced as solid, mixture of solid and water e.g sewerage, liquid and gases from residential housing, manufacturing industries/factories, resources extraction projects such as in mining, logging, oil and gas development projects, road constructions, forms.
All human activities on the earth produce waste products. Theses wastes are identified by their source of origin such as domestic wastes, hospital wastes and industrial wastes. So wastes are identified by their source of origin as mentioned and by some other names making references to their origins. Sometimes more specific terms are used such as mining wastes, logging wastes, office wastes and the list goes on.
Let us look at domestic wastes and industrial wastes. Domestic wastes are generated from residential households, schools, educational institutions, offices and other places where people commute. Industrial wastes are associated with industries such as mining, oil and gas projects, logging, fish processing plants, mechanical workshops, shops, super markets, hotels, shipping, fish and meat canneries. Hospital wastes do not fall into these categories and are treated separately as special wastes due to their origins and composition. Wastes are identified by their source of generation, their physical state such as solid, liquid, sewerage, wastewater and gases. The wastes are also identified by their composition such as being hazardous, toxic, acidic or alkaline.
I would like to focus my discussion on the wastes generation from the mining industry. Mines in Papua New Guinea such as the Porgera, Ok Tedi, K92, Lihir, Misima, Hidden Valley, Ramu Nickel and Freda River Copper Mine. The waste stream from the mining industry has brought about a lot of concerns, discussions on mine tailings as an example of industrial wastes.
Mine tailings
Let use identify some reasons why there are so many discussions and concerns raised when it comes to mine tailings disposal. To analyse these issues, let us identify what mine tailings are, their composition and their impacts on the environmental and human health.
Tailings are different from overburden, which are the waste rocks or other material that overlies an ore or mineral body and is displaced during mining. Tailings are a by-product of mining. After ore containing an economically – recoverable commodity is mined from the earth, that commodity is extracted in a processing plant or mill. After this commodity of value is extracted from the ore material, the resultant waste stream is termed “tailings”.
Tailings – consist of crushed rocks, water, trace quantities of metals such as copper, mercury, cadmium, zinc, etc – additives used in processing such as petroleum byproducts, sulfuric acid and cyanide
Tailings type – in addition to being classified as hazardous according to UNEP, their large volumes require environmental measures to optimise the management of these types of wastes
Tailings can contaminate aquatic life with toxic heavy metals and milling chemicals. Some metals, particularly mercury, may bioaccumulate up the food chain, ultimately harming humans. It causes turbidity (suspended particulates) and reduces oxygen levels which directly impacts aquatic life.
When rain falls on tailings, it leaches away materials that can create water pollution, for example, lead, arsenic, and mercury. Sulfuric acid is sometimes produced when water interacts with tailings, or it can be a by-product of ore processing.
The flow of tailings burying aquatic and riparian nursery habitats and the persistence of heavy- metal contamination have also been shown to negatively affect the regenerative capacity of aquatic and terrestrial ecosystems, leading to long term changes in ecosystem structure and functions.

Tailings dam failure impacts
The impacts of tailings dam failures on biodiversity can be both immediate and long term. When large volumes of tailings enter waterways, the material can have physical (e.g increased turbidity, smothering) and chemical (e.g, toxicity from toxic contaminates, decreased oxygen) impacts on aquatic organisms. The type and location of the failure is, however, an important factor in the severity and extent of these impacts.
The impacts of these tailings dam failures on biodiversity are immediate, in terms of smothering habitats and contaminating waterways. Aquatic life is heavily impacted due to the extreme change in water chemistry. The suspended solids that are introduced can get trapped in fish gills, with flow-on effects on semi-aquatic and terrestrial species. The flow of tailings burying aquatic and riparian nursery habitats and the persistence of heavy- metal contamination have also been shown to negatively affect the regenerative capacity of aquatic and terrestrial ecosystems, leading to long-term changes in ecosystem structure and functions.
This severity impacts the services these ecosystems provide to people, such as flood defense, erosion control and soil stability, water purification and regulation, nutrient cycling and carbon storage.
While the direct human costs of tailings dam failures are quantified, the long-term social costs in terms of poor health, and loss of income and livelihoods that result from a degraded environment, remain largely unknown.
Tailings conditions of failures
Tailings facilities/dams with access water storage have a higher risk of failure as they are more susceptible to overtopping, piping and liquefaction failures. I addition, they pose greater failure consequences as the saturated conditions will lead to more material being mobilized.

Tailings disposal and management
If not managed properly, tailings can have chronic adverse impacts on the environment and human health and safety, with pollution from effluent
To limit the potential for this material to generate acid and metalliferous drainage, best practice waste management will include subaqueous deposition of the mine waste rock and tailings in the engineered ISF, located downstream of the mine site
Keeping the tailings and potential acid forming waste rock permanently submerged under all foreseeable conditions. This is important because the geochemical characterization of the waste rock and tailings shows that the material would become acid-forming if exposed to atmospheric conditions over short to medium timeframes, with potential impacts to downstream water quality
Discussions on mine tailings will continue in the next few articles.

• The author is the principal scientist at Yeyue Environmental Services