Answers to Environmental Studies Questions

Biogas typically refers to a mixture of different gases produced by the breakdown of many organic matter in the absence of some oxygen. Biogas can be produced from regionally available raw materials such as recycled waste. It is a renewable energy source and in many cases exerts a very small carbon footprint.

Biogas is produced by anaerobic digestion with anaerobic bacteria or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops. It is primarily methane and carbon dioxide and may have small amounts of hydrogen sulphide, moisture and siloxanes.

The gases methane, hydrogen, and carbon monoxide can be oxidized with oxygen. This energy release allows biogas to be used as a fuel; it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.

Biogas can be compressed, the same way natural gas is compressed to CNG, and used to power motor vehicles. In the UK, for example, biogas is estimated to have the potential to replace around 17% of vehicle fuel.

Solar desalination is a technique to desalinate water using solar energy. There are two basic methods of achieving desalination using this technique; direct and indirect.
In the direct method, a solar collector is coupled with a distilling mechanism and the process is carried out in one simple cycle. Water production by direct method solar distillation is proportional to the area of the solar surface and incidence angle. Because of the relatively high cost of property and material for construction direct method distillation tends to favor plants with production capacities less than 200m3/day.

Indirect solar desalination employs two separate systems; a solar collection array, consisting of photovoltaic and/or fluid based thermal collectors, and a separate conventional desalination plant. Production by indirect method is dependent on the efficiency of the plant and the cost per unit produced is generally reduced by an increase in scale. Many different plant arrangements include but are not limited to Multiple Effect Humidification (MEH), Multiple Stage Flash Distillation (MSF), Multiple Effect Distillation (MED), Multiple Effect Boiling (MEB), Humidification Dehumidification (HDH), Reverse Osmosis (RO), and Freeze effect distillation.

Eco-labeling Eco-labels and Green Stickers are labeling systems for food and consumer products. Ecolabels are voluntary, but green stickers are mandated by law. They are a form of sustainability measurement directed at consumers, intended to make it easy to take environmental concerns into account when shopping. Some labels quantify pollution or energy consumption by way of index scores or units of measurement; others simply assert compliance with a set of practices or minimum requirements for sustainability or reduction of harm to the environment.

Ecolabelling systems exist for both food and consumer products. Both systems were started by NGOs, since then the European Union have developed legislation for conduct of ecolabelling and also have created their own ecolabels, one for food and one for consumer products. Label trust is an issue for consumers.