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Why do two towns that use different energy sources have such different air, water, and land around them?
A group of fourth-grade scientists visited both towns and recorded what they noticed. In Coalville, the sky often had a hazy, grayish look, and some of the nearby pond water had an oily film on the surface. In Sunfield, the sky was clear and blue, and the ponds nearby were clean enough for swimming. The students also noticed that Coalville's power plant had large piles of ash near it, and trucks delivered loads of coal every day.
The students wondered: If these two towns are so similar, why does the environment around them look so different?
People need energy to heat homes, power lights, run cars, and cook food. But where that energy comes from — the energy source — makes a big difference for the environment around us. Scientists have studied many types of energy sources and their environmental effects (the changes they cause in air, water, land, and living things). Some energy sources cause more pollution and damage than others.
Energy sources can be sorted into two main groups. Nonrenewable energy sources are resources that take millions of years to form and will eventually run out. These include coal, oil (petroleum), and natural gas — all called fossil fuels because they formed from ancient plants and animals. Renewable energy sources are resources that nature replaces quickly or that will not run out. These include solar energy (sunlight), wind energy, and hydroelectric energy (moving water).
Scientists who study energy and the environment don't just look at one measurement — they gather information from many sources and compare the data. They measure things like the amount of CO₂ released per unit of energy, the amount of land disturbed, the effect on water quality, and the impact on wildlife. Then they organize this information into comparison charts and tables to help people make informed decisions.
In this investigation, we will act like environmental scientists. We'll examine data about four common energy sources and compare their effects on air, water, and land. A fair comparison means looking at the same categories for each energy source so we can spot the differences clearly.
Materials scientists might use:
Below is a data table that environmental scientists might create after gathering information about four energy sources. Study the table carefully — this is the kind of evidence scientists use to compare environmental effects.
| Energy Source | Type | Air Pollution | Water Effects | Land Effects |
|---|---|---|---|---|
| Coal | Nonrenewable | High — releases CO₂, soot, and harmful gases | Coal ash and chemicals can wash into water | Mining digs up large areas; ash piles take up land |
| Natural Gas | Nonrenewable | Medium — releases CO₂, but less soot than coal | Drilling can affect groundwater | Drilling pads and pipelines change the landscape |
| Solar | Renewable | Very low — no emissions during operation | Minimal water use; no chemical runoff | Solar farms need large open areas |
| Wind | Renewable | Very low — no emissions during operation | Minimal — no water used during operation | Turbines need space; can affect birds and bats |
Look at the bar chart above. Notice how the bars for coal and natural gas are much taller than the bars for solar and wind. This pattern in the data tells us that fossil fuels release far more CO₂ into the air than renewable energy sources. This is one of the most important differences scientists have found when comparing the environmental effects of energy choices.
Now let's go back to our two towns and use what we've learned. Coalville's power plant burns coal every day. When coal burns, it releases carbon dioxide (CO₂), sulfur dioxide, soot particles, and other pollutants into the air. That's why the sky looked hazy. The ash left over from burning coal piles up on the ground, and rain can wash chemicals from that ash into nearby ponds and streams — which explains the oily film on the water.
Sunfield's solar panels, on the other hand, work by capturing sunlight and turning it directly into electricity. There is no burning involved, so there are no smoke, no ash, and no chemical runoff during operation. That's why Sunfield's air is clear and its ponds are clean. However, the solar farm does use a large area of land that could have been a field or forest, so it does have some environmental effect — just a different kind.
Scientists have also found that the environmental effects go beyond what we can see. Burning fossil fuels adds extra CO₂ to the atmosphere, which acts like a blanket around the Earth and contributes to climate change — a gradual warming of our planet's temperature. This can lead to more extreme weather events, rising sea levels, and changes in habitats for plants and animals.
The flowchart above shows an important idea: no energy source is completely "free" of environmental effects. Even renewable energy sources affect the land and can sometimes affect wildlife. But the data shows that fossil fuels cause significantly more pollution to air, water, and land than renewable energy sources do. This is the kind of evidence that helps communities, engineers, and governments make informed decisions about which energy sources to use.
One of the most important ideas in science is cause and effect. Scientists look for what causes something to happen, and what the effects (or results) are. When we compare energy sources, we can clearly see cause-and-effect relationships. The cause is the type of energy source and how it works. The effect is what happens to the air, water, and land.
This same pattern — where different choices lead to different effects on the environment — shows up in many areas of science, not just energy. Let's look at some examples:
| Area of Science | The Cause (Choice or Action) | The Effect (What Happens) |
|---|---|---|
| Energy | Burning coal for electricity | CO₂ and soot in the air; ash on the ground |
| Energy | Using solar panels for electricity | Clean air; land used for panels |
| Transportation | Driving gasoline cars | Exhaust fumes pollute the air |
| Transportation | Riding bicycles or electric buses | Much less air pollution |
| Farming | Using chemical fertilizers on crops | Chemicals can wash into rivers and harm fish |
| Farming | Using natural compost on crops | Less chemical runoff; healthier soil |
Do you see the pattern? In each example, when people choose an option that involves burning fuel or using chemicals, the effect on the environment tends to be greater. When people choose options that work with natural processes or produce less waste, the effect on the environment tends to be smaller. This cause-and-effect pattern repeats across many areas of science and helps us predict what might happen when we make different choices.
All around the world, communities are using science to make important decisions about energy. Engineers and scientists work together to design solutions that meet people's energy needs while reducing harmful effects on the environment. This is a real-world engineering design challenge: How can we provide enough energy for everyone while keeping the air, water, and land as healthy as possible?
Here are some real examples of how people are using this science:
When engineers design energy solutions, they consider trade-offs — the idea that solving one problem might create a different, smaller problem. For example, a solar farm produces clean electricity (solving air pollution), but it takes up a lot of land (creating a different effect). Engineers try to find the best balance.