ENSC 1: Introduction to Environmental Science - Fossil Fuels PDF

http://www.markusreugels.de/liquidart ENSC 1: Introduction to Environmental Science Session 14 Fossil fuels Recap and forecast Last time: Overall energy usage patterns and trends Today: Fossil Fuels Coal Oil Natural Gas U.S. Energy Policy Objective 1: Increase Energy Efficiency...

http://www.markusreugels.de/liquidart ENSC 1: Introduction to Environmental Science Session 14 Fossil fuels Recap and forecast Last time: Overall energy usage patterns and trends Today: Fossil Fuels Coal Oil Natural Gas U.S. Energy Policy Objective 1: Increase Energy Efficiency and Conservation Requires many unpopular decisions because need to balance short term loss with long term gain Example: decrease speed limit to conserve fuel Objective 2: Secure Future Fossil Fuel Energy Supplies Domestic sources 3 concerns: security, environmental, and economic Objective 3: Develop Alternative Energy Sources Recent policy changes: Consumers to sell energy back to grid Better pricing of alternate sources Who should pay for this? Gas taxes? Objective 4: Meet the First Three Objectives Without Further Damage to the Environment Tax fossil fuel use per barrel? Energy Policy and Climate Change Fossil fuels account for ~80% of global energy consumption Any policy that addresses climate change must therefore be an energy policy Problem: benefits of fossil fuel extraction and combustion are immediate and localized, while negative consequences are long term and widespread Immediate individual incentives push towards more fossil fuel consumption, not less! (Tragedy of the Commons situation) Well-designed policies could promote commitments to technologies and practices with long-term benefits World energy consumption by source shows overall trends Steady increases in global energy demand over past century General dominance of fossil fuels, though renewables showing recent increases Rise of fossil fuels can be seen in data going back to start of industrialization “Traditional biomass” = mostly wood burning First coal, then oil, then natural gas have rapidly replaced wood Fossil Fuels: energy-dense hydrocarbons composed of the remnants of prehistoric organisms that existed millions of years ago Includes coal, oil (petroleum) and natural gas Supply over 80% of energy used in North America Non-renewable resource: created too slowly to replace reserves at the pace we use them Current fossil fuels began roughly 300 million years ago Sun was cooler (~3% less intense) Different continental structure led to less warming than present day (Pangaea) CO2 levels were typically much higher to compensate, keeping climate relatively mild Periods of dramatic climate changes did occur, on timescales of perhaps tens of thousands of years These “rapid” climate changes are typically linked to loss of diversity in the fossil record, indicating large scale extinction events Fossil Fuel formation specifics Coal: Heat, pressure, and time turn nondecomposed solid terrestrial plant material into carbon-rich rock Oil: Originally was mostly algae, bacteria, and simple aquatic plants, preserved and concentrated over time Natural Gas: Origins similar to oil, but at much higher temperatures and pressures, causing organic material to break down into smaller, simpler hydrocarbons Review: the carbon cycle Carbon naturally cycles between biosphere, hydrosphere, and atmosphere Fossil fuels represents a longterm storage of carbon that has been removed from circulation over hundreds of millions of years Fossil fuel combustion Burning releases that C as CO2 Without any natural process to quickly return that carbon to the ground, this represents a massive, sudden, and irreversible transfer Reminder: the Sun and Earth were Fossil fuels both completely different the last time this old carbon was in the air! Numbers are expressed as 1015 g of carbon Coal: A black, combustible solid composed mainly of carbon, water, and trace elements found in Earth’s crust Most coal deposits are believed to have been identified Occurs in different grades- based on variations in heat and pressure during burial Quality measured in energy density – energy per volume Highly flammable, dangerous to mine Burning and mining both release pollutants ~90,000 accidental miner deaths during 20th century Increased risk of lung disease and cancer: estimated 2,000 more miner deaths each year from related diseases Coal availability by country U.S. has ~24% of world’s estimated coal supplies Established, proven coal reserves could last ~130 years at present rate of consumption Vast majority burned for electricity generation Fraction of coal contributions to total energy by country Coal dominant energy source in some parts of the world, but usage is declining overall in most countries Overall relative importance of coal to US energy has been dropping since 2008 Coal dominant energy source in some parts of the world, but usage is declining overall Contribution to total energy in the US dropped below 10% in 2023 for the first time in 100 years Surface mining of coal Coal usually found in seams that vary from 1in to 100 ft in thickness Surface mining chosen if coal is within 100 ft of surface Strip mining refers to practice of digging trenches along surface seams to extract resources (like coal) Highly destructive of local environments, though relatively safe for miners Mountaintop removal mining: a form of surface mining in hilly, mountainous regions Layers of mountain cleared away to reach seams below Mountaintop removal mining: a form of surface mining in hilly, mountainous regions Layers of mountain cleared away to reach seams below “Overburden” or leftover rock and soil often dumped into valleys, lakes, and streams Subsurface mining of coal Extraction of mineral and energy resources from deep underground deposits Makes up ~40% of current coal mining operations More expensive and less safe than surface mining However, less destructive to landscapes than surface mining https://idahocapitalsun.com Atmospheric impacts of coal combustion Coal often contains high concentrations of sulfur and nitrogen which are released on combustion Resulting emissions of NOx (NO and NO2) and SOx (SO2 and SO3) can then contribute to pollutant formation and acid rain “Clean coal” refers to efforts (in US often associated with 1990 Clean Air Act Amendments) to reduce NOx and SOx emissions, for example by adding components that react with and remove undesired compounds Note that these technologies do not necessarily reduce CO2 emissions! CO2 emissions from coal have been increasingly targeted 2014 US Supreme Court decision allowed EPA to regulate CO2 emissions Has slowly pressured oldest and least efficient plants to close, pending upgrades that include carbon capture technologies Decline of coal also market-driven: recent improvements in efficiency of natural gas extraction makes it far more competitive economically compared to the risk and cost of coal mining Oil and Natural Gas Exploration Oil and natural gas tend to migrate upwards until they hit impermeable rock Usually located in underground geologic structures that tend to trap any oil or natural gas, if present Extraction and refining technologies Refining separates numerous hydrocarbons present in crude oil (petroleum) Refining process and eventual use depends on boiling point Natural gas contains far fewer hydrocarbons than crude oil, making it tend to burn cleaner Oil and Natural Gas extraction and consumption Liquid forms of energy are more versatile, easier to transport, cleaner to burn Oil and gas together provide ~62% of U.S. energy, and ~55% of world’s energy Oil: massive fraction of energy in many countries worldwide Liquid forms of energy are more versatile, easier to transport, cleaner to burn Oil and gas together provide ~62% of U.S. energy, and ~55% of world’s energy Oil alone still makes up a large fraction of energy production, especially in oil-rich countries US fractional contribution of oil slowly declining Liquid forms of energy are more versatile, easier to transport, cleaner to burn Oil and gas together provide ~62% of U.S. energy, and ~55% of world’s energy Oil alone still makes up a large fraction of energy production, especially in oil-rich countries In US, oil peaked in fractional contribution at nearly 50%, slow decline since 1980s Natural gas: significant global contributor, recent increases related to new extraction techniques Currently at roughly 33% total US energy Natural gas: significant global contributor, recent increases related to new extraction techniques Currently at roughly 33% total US energy Showed slow decline in domestic fractional contribution until 2006, when newer extraction technologies led to a huge boost in availability (fracking) Natural gas composition is mostly made up of simple gas- phase hydrocarbons Contains gases such as methane, Raw natural gas ethane, propane, and butane Propane and butane are typically extracted and sold for cooking and heating Methane then used for heat and to generate electricity in power plants Natural gas increasingly used for Pipeline natural gas electricity, transportation, and commercial cooling In vehicles, emits 93% fewer hydrocarbons, 90% less carbon monoxide and 90% fewer toxic emissions than gasoline Hydraulic fracturing (fracking) brought a massive boost to US natural gas availability in mid 2000’s Many natural gas reserves are bound up in layers of brittle rock By blasting these layers with mixtures of pressurized liquid and sand they can be fractured and held open, allowing trapped natural gas to be extracted Hydraulic fracturing (fracking) brought a massive boost to US natural gas availability in mid 2000’s General diagram of hydraulic fracturing site Well head Many natural gas reserves where fracturing are bound up in layers of fluids are injected brittle rock By blasting these layers with mixtures of pressurized liquid and sand they can be fractured and held open, Source: US EPA (2012) allowing trapped natural gas Active hydraulic fracturing site to be extracted Extraction process can have major impacts on local environment, including water Pit for storing recovered wastewater Source: fracfocus.org Many potential impacts on local drinking water Emissions of natural gas or fracturing fluid into groundwater supplies can occur through multiple pathways Faulty or Well leakage Fluid connection damaged wells can leak into groundwater aquifers Fracturing can also be too successful, opening up cracks that directly connect reservoirs with groundwater Many unknowns about fracturing fluid composition and health effects, making regulation especially difficult Fluid is mostly water, with additives to assist with extraction Many unknowns about fracturing fluid composition and health effects, making research and regulation especially difficult Fluid is mostly water, with additives to assist with extraction Exact mixtures are proprietary and therefore not publicly available information http://www.epa.gov/hfstudy