UPSC Prelims 2022 Q49: Biorock Technology — Explained
"Biorock technology" is talked about in which one of the following situations?
- Restoration of damaged coral reefs
- Development of building materials using plant residues
- Identification of areas for exploration/extraction of shale gas
- Providing salt licks for wild animals in forests/protected areas
Answer: (a) Restoration of damaged coral reefs
Statement-wise explanation
- a: correct — Biorock, also called mineral accretion, runs a low-voltage direct current through seawater between a steel frame (the cathode) and an anode. Dissolved minerals, mainly calcium carbonate as aragonite and magnesium hydroxide as brucite, are deposited on the frame as a limestone-like coating. Fragments of broken coral are tied to this frame and grow on it. In January 2020 the Zoological Survey of India (ZSI), working with the Gujarat Forest Department, placed a biorock structure off Mithapur in the Gulf of Kachchh. It was India's first trial of the method for restoring damaged reefs.
- b: incorrect — Building materials made from plant residues include agro-waste bricks, hempcrete and boards made from straw or bagasse. They are not linked to biorock. Wolf Hilbertz did first develop mineral accretion in the 1970s as a building material, which is the trap here. But that material grows from minerals dissolved in seawater, not from plant matter.
- c: incorrect — Shale gas is natural gas trapped in fine-grained shale rock. Areas for it are found through geological and geophysical surveys, and the gas is extracted by horizontal drilling and hydraulic fracturing. Biorock has no role in this work.
- d: incorrect — A salt lick is a natural or man-made deposit of salts and minerals that herbivores lick to meet their mineral needs. Forest managers in protected areas sometimes provide them. They have nothing to do with electrolysis of seawater or biorock.
How to eliminate
This is a pure fact-recall question: you either know biorock or you reason from the word. 'Bio' plus 'rock' suggests living things growing on a rock-like base, and a coral reef is exactly that: living polyps on a limestone skeleton. Shale gas exploration is geology, not biology, and salt licks are not rock 'grown' biologically. That leaves the coral and plant-residue options. Plant-residue materials are usually named for their raw material (agro-waste, bagasse, hemp), not 'rock'. The fact to remember: Biorock = mineral accretion = low-voltage current through seawater lays limestone on a steel frame on which corals are grown. India's trial was run by ZSI off Mithapur, Gulf of Kachchh, in 2020.
Know more
How Biorock works
A steel frame is placed on the seabed and wired as the cathode. A separate anode completes the circuit, and a low-voltage direct current is passed through, often from solar panels floating at the surface. Electrolysis of seawater raises the pH near the cathode. Dissolved calcium and magnesium are then deposited on the frame as aragonite (calcium carbonate, the same mineral as coral skeletons) and brucite (magnesium hydroxide). Lower current gives slower but harder aragonite. Higher current gives faster but softer, brucite-rich deposits. Coral fragments tied to the frame do not have to spend as much energy building a skeleton, so they can put more energy into growth.
Wolf Hilbertz, an architect, developed the process in the 1970s as a way to 'grow' building material from seawater. Thomas Goreau later worked with him to apply it to reef restoration.
Reef restoration methods compared
| Method | What is done |
|---|---|
| Coral transplantation / translocation | Live colonies or fragments are moved from a donor or threatened site to a degraded one |
| Coral gardening | Fragments are grown in nurseries, then planted out on reefs |
| Artificial reefs | Concrete or steel structures give corals and fish a hard surface to settle on |
| Biorock (mineral accretion) | Electrified steel frames grow a limestone crust on which corals are fixed |
India's reef areas
India's four major coral reef areas are the Gulf of Mannar, the Gulf of Kachchh, Lakshadweep, and the Andaman and Nicobar Islands. According to a 2024 parliamentary reply, ZSI monitors these reefs and does coral restoration and transplantation work. Reefs need restoring mainly because of bleaching caused by marine heatwaves, as well as sedimentation, pollution and destructive fishing.
In the news
In January–February 2020, news reports covered ZSI and the Gujarat Forest Department starting India's first biorock trial off Mithapur in the Gulf of Kachchh. That made the term a current-affairs item before the 2022 paper.
NCERT Concepts to Revise
- Coral bleaching: Bleaching is a main cause of the reef damage that restoration techniques try to repair.
- Shale gas: One option is about shale gas; knowing what it is and how it is found helps you judge that option.