tank

Scrubbers to clean up shipping

May 1, 2025 By EarthWise Leave a Comment

Cargo ships are significant sources of global air pollution because of their fuel oil. Most ships burn heavy fuel oil that is loaded with sulfur, so when it is burned it produces noxious gases and fine particles that can harm human health and the environment. The International Maritime Organization enacted a mandatory cap of 0.5% for the sulfur content of marine fuels in 2020. Heavy fuel oil has a sulfur content of 2 to 3 percent.

Shipping companies can comply by burning low-sulfur fossil fuels or biofuels, but these are much more expensive. The most feasible and cost-effective option is to install exhaust gas cleaning systems, known as scrubbers.

A scrubber is a huge metal tank installed in a ship’s exhaust stack. Seawater is sprayed from nozzles to wash the hot exhaust. The seawater reacts with sulfur dioxide and converts it to sulfates, which are environmentally benign natural components in seawater.

A study by the National Technical University of Athens in Greece has performed a lifecycle assessment of the use of scrubbers and has found that burning heavy fuel oil with the use of scrubbers can match or even surpass the benefits of using low-sulfur fuels.

Producing low-sulfur fuel causes additional greenhouse gas and particulate matter emissions in refineries. On the other hand, scrubbers reduce sulfur dioxide emissions by 97% and dramatically reduce other pollutants as well.

The study shows the importance of incorporating lifecycle assessments into evaluation of environmental impact reduction policies.

**********

Web Links

Study: Burning heavy fuel oil with scrubbers is the best available option for bulk maritime shipping

Photo, posted August 3, 2015, courtesy of Lotsemann via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Hydrogen-powered aviation

December 16, 2024 By EarthWise Leave a Comment

The transportation sector is responsible for about a quarter of human-generated greenhouse gas emissions. Most of the energy used by transport systems comes from fossil fuels. The transition to electric vehicles – cars, trucks, and buses – is making a real difference. However, the emissions from the aviation industry have continued to grow faster than those of other forms of transportation. There have been increased efforts to develop hydrogen-powered aircraft, but the challenges are substantial.

Hydrogen can be used for aviation both as a directly combusted fuel, or to power electric fuel cells. Its advantages are that its use produces no carbon dioxide, and, in fact, hydrogen produces more energy per pound than jet fuel.

A study by researchers at MIT looked at the prospects for hydrogen use in aircraft and what needs to be done to make it practical. The biggest issue is that the extra bulk of a hydrogen fuel tank and fuel cells in a plane would have to be offset by weight reductions elsewhere, such as reducing payload (cargo or passengers). This would mean there would need to be more flights, thereby reducing the gains made. The researchers argued that improvements in fuel cell power and more weight efficient fuel systems could eliminate the need for additional flights.

The bigger challenge is the infrastructure for generating and distributing hydrogen. There needs to be green hydrogen – hydrogen produced without carbon emissions – and the infrastructure for getting it to planes where it is needed has to also not produce substantial emissions.

The study suggests that the rollout of hydrogen-based aviation should start at locations that have favorable conditions for hydrogen production.

**********

Web Links

Fueling greener aviation with hydrogen

Photo, posted December 20, 2016, courtesy of Dylan Agbagni via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Solar-Powered Desalination | Earth Wise

September 6, 2022 By EarthWise Leave a Comment

About two-thirds of humanity is affected by water shortages. In the developing world, many areas with water shortages also lack dependable sources of electricity. Given this situation, there is widespread research on using solar heat to desalinate seawater. To date, many approaches to this face problems with fouling of equipment with salt buildup. Tackling this issue has proven to add complexity and expense to solar desalination techniques.

A team of researchers from MIT and China has recently developed a solution to the problem of salt accumulation that is more efficient than previous methods and is less expensive as well.

Previous attempts at solar desalination have relied on some sort of wick to draw saline water through the device. These wicks are vulnerable to salt accumulation and are difficult to clean. The MIT-Chinese team has developed a wick-free system instead. It is a layered system with dark material at the top to absorb the sun’s heat, and then a thin layer of water that sits above a perforated layer of plastic material. That layer sits atop a deep reservoir of salty water such as a tank or pond. The researchers determined the optimal size for the holes in the perforated plastic.

The 2.5 millimeter holes are large enough to allow for convective circulation between the warmer upper layer of water above the perforated layer and the colder reservoir below. That circulation naturally draws the salt from the thin layer above down into the much larger body of water below.

The system utilizes low-cost, easy to use materials. The next step is to scale up the devices into a size that has practical applications. According to the team, just a one-square-meter system could provide a family’s daily needs for drinking water.

**********

Web Links

Solar-powered system offers a route to inexpensive desalination

Photo, posted February 13, 2017, courtesy of Jacob Vanderheyden via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Hunt For Marine Plastic | Earth Wise

December 21, 2021 By EarthWise Leave a Comment

Estimates are that about 10 million tons of plastic enter the ocean every year. This is equivalent to a truckload of plastic being dumped into the sea every minute and the stuff is not easy to keep track of. Some of it ends up in the infamous ocean garbage patches. But overall, researchers only know what happens to about 1% of it.

The European Space Agency has decided to find out whether it might be possible to detect and track floating plastic in the oceans using satellite monitoring. Researchers have a variety of ideas about how best to do this and now the agency is testing some of those ideas.

The ESA maintains something called the Atlantic Basin Facility which is a 7000 square-foot tank equipped to simulate various types of waves and tidal currents. It is the largest facility of its kind in the world.

Researchers place plastic in the basin consisting of typical items found at sea, such as bags, bottles, marine nets and ropes, plastic cutlery, and Styrofoam balls. The plastic used in the study included material previously recovered from the sea through ocean cleanup campaigns. Multiple research groups from European universities used specialized instrumentation to monitor the basin from above. Techniques included radar remote sensing, something called GNSS reflectometry, and specialized optical instrumentation.

Initial results look promising in that under some circumstances teams received useable signals. It will take further analysis to determine the ultimate utility of space-based monitoring of plastic entering the ocean. Marine litter is a large and growing problem. Figuring out where it all is and where it is going is a necessary part of any solution.

**********

Web Links

Hunting for marine plastic

Photo, posted March 24, 2017, courtesy of Holly Richards/USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A New Fishway Technology | Earth Wise

February 5, 2021 By EarthWise Leave a Comment

Freshwater fish populations have declined by more than 80% over the past forty years across the globe. This is in part due to hundreds of thousands of dams, weirs, and barriers stopping their movements. These river barriers have disrupted fish reproduction cycles the world over by preventing river fish from migrating to spawn.

Fishways or fish ladders are waterways constructed on or around obstructions in order to provide passageways for fish and other aquatic species. Often, they consist of a series of small overflow weirs and pools constructed in the form of steps. Fish need to jump from one pool to another to migrate to the upstream. Such fish ladders require a large space to construct. These and several other types of fishways tend to be expensive to install and maintain and are not always successful in allowing fish to get to where they need to go.

Researchers at the University of New South Wales in Australia have come up with an ingenious new type of fishway. Called a “tube fishway”, it is a low-cost and low-energy installation that works by pumping fish at high velocity – protected by a cushion of bubbly water – through a tube running over the obstructing barrier to deliver them safely into the water on the other side.

They successfully demonstrated a prototype system on a rugged slope behind a campus building that transported fish from one tank to another about 25 feet up the slope.

Fish are attracted into the chamber by suitable geometry and the system uses the energy available from the upper reservoir to lift the fish. Modeling shows that the system will work for pipes as large as three feet in diameter and could lift fish more than 300 feet vertically.

**********

Web Links

New fishway technology to get fish up and over those dam walls

Photo, posted October 19, 2019, courtesy of Andrew Harvey via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fitness Trackers For Lobsters | Earth Wise

October 20, 2020 By EarthWise Leave a Comment

The lobster industry is somewhat unique, at least in this country, in that it involves an animal food that is kept alive until it has reached the destination where it will be consumed or used. As a result, the industry has to deal with a problem they call “shrink”, which is the mortality lobsters experience as they change hands from capture to kitchen.

Maine’s lobster industry has reached out to the University of Maine Lobster Institute along with collaborators at other institutions to help quantify and mitigate stress points in the lobster supply chain that reduce survival and profitability.

A 2-year project was funded by the National Oceanic and Atmospheric Administration to create miniature sensory devices – crustacean heart and activity trackers (called C-HATs). These are essentially Fitbits for lobsters. The noninvasive devices strapped on a lobster monitor its heart rate and movement as it passes from trap to on-board live tank to live storage crate to truck to wholesaler to retailer or processor.

A separate sensor-equipped device called the MockLobster travels along with the lobsters to log environmental conditions experienced, including temperature, light and dissolved oxygen levels.

The hope is to be able to get a good handle on the conditions lobsters experience from trap to market and learn where problems are likely to arise. The researchers are also working to develop economical, standardized protocols to monitor water quality and the heath of lobsters during their movement through the supply chain.

The goal is to produce big improvements in the bottom lines of everyone along the supply chain along with big improvements in the health of the lobsters destined for market.

**********

Web Links

Fitness trackers, environmental sensors prototyped to improve survival in the lobster supply chain

Photo, posted August 29, 2015, courtesy of Adam Grimes via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Toyota’s Hydrogen Factory

January 15, 2018 By EarthWise 2 Comments

Toyota is one of several automakers that are promoting hydrogen fuel cell cars – electric cars that get their energy from fuel cells rather than batteries. Fueling one of these cars is much like filling up the tank of a gasoline-powered car, except that the fuel in question is hydrogen.

A Hydrogen Sponge

April 7, 2017 By EarthWise

Hydrogen fuel cell electric vehicles are just starting to enter the market but they have a long way to go before they can even catch up with their battery-powered counterparts. Powering cars with hydrogen has the advantage that fueling the vehicle is much like what we are used to: pull up to the pump, fill your tank for a few minutes, and drive off.

[Read more…] about A Hydrogen Sponge