Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 14: Problem 7

If \(50 \mathrm{~kJ}\) of energy are spent to extract \(1 \mathrm{MJ}\) of energy content in the form of coal, what is the EROEI?

Short Answer

Expert verified
Answer: The EROEI for extracting coal is 20.

Step by step solution

01

Convert all energy values to the same unit

We have the invested energy in kJ and the extracted energy in MJ. To calculate the EROEI, we need to have both energy values in the same unit. We will convert the extracted energy from MJ to kJ. 1 MJ = 1000 kJ
02

Calculate the EROEI

To find the EROEI, divide the energy extracted by the energy invested: EROEI = \frac{Energy\: Extracted}{Energy\: Invested} EROEI = \frac{1000 \mathrm{~kJ}}{50 \mathrm{~kJ}} EROEI = 20 The EROEI of the coal extraction is 20. This means that for every 1 unit of energy invested in the extraction process, 20 units of energy are obtained from coal.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

The U.S. gets \(2.4\) qBtu per year of energy from burning biomass (mostly firewood). At an energy density of 4 kcal per gram, and a population of 330 million, how many 5 kg logs per year does this translate to per person?

Replicate the conclusion of Box \(14.3\) by assuming one-quarter of the 2 trillion tons \(\left(5 \times 10^{1} 4 \mathrm{~kg}\right)\) of mass is combustible at \(4 \mathrm{kcal} / \mathrm{g}\). How long-in years-would this amount of energy last if burning at 18 TW?

Re-express an EROEI of \(1.5: 1\) in terms of how many total units of energy must be produced in order to extract one unit of net energy in a self- supporting operation.

A large tree might have a trunk \(0.5 \mathrm{~m}\) in diameter and be \(40 \mathrm{~m}\) tall. Even though it branches out many times, pretend all the wood fits into a cylinder maintaining this \(0.5 \mathrm{~m}\) diameter for the full height of the tree. Wood floats, \({ }^{33}\) so let's say it has a density around \(800 \mathrm{~kg} / \mathrm{m}^{3}\). How many kilograms of \(\mathrm{CO}_{2}\) did this tree pull out of the atmosphere to get its carbon, if we treat the tree's mass as \(50 \%\) carbon?

Our modern food industry has an EROEI of 0.1:1. In pre-industrial settings, when energy investment for food production was in the form of muscle power (animal and human), why would a 0.1:1 EROEI for food have been untenable? Next, describe the conditions for an exact break-even food EROEI of 1:1. What would this mean in terms of where effort/energy goes? What would this leave for building shelters, cathedrals, or esthetic pursuits?
See all solutions

Recommended explanations on Environmental Science Textbooks

Physical Environment

Read Explanation

Ecological Conservation

Read Explanation

Biological Resources

Read Explanation

Environmental Research

Read Explanation

Living Environment

Read Explanation

Energy Resources

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free