Beirut Blast: How does yield of 2,750 tonnes of ammonium nitrate compare against Halifax explosion, Hiroshima bombing?

In one of the biggest non-nuclear explosions, 2,750 tonnes of ammonium nitrate, used in fertilisers and bombs, destroyed part of the Lebanese capital Beirut on Tuesday. The massive blast at Beirut port killed at least 100 people and injured nearly 4,000. 

The mushroom cloud into the sky was seen from kilometres and captured in dramatic footage. The blast flattened the city in a radius of several miles, with the rescue workers still digging through the mangled wreckage of buildings and looking for survivors.

Reuters reported that the intensity of the blast threw victims into the sea where rescue teams tried to recover bodies. 

Extraordinary footage of the explosion of Beirut. pic.twitter.com/yBEGzwYeGv

— Saad Mohseni (@saadmohseni) August 4, 2020

According to the Lebanese authorities, the blast was caused by improper storage of 2,750 tonnes of ammonium nitrate. The potential explosive had been stored for six years at the port without safety measures.

President Michel Aoun said the government was "determined to investigate and expose what happened as soon as possible, to hold the responsible and the negligent accountable, and to sanction them with the most severe punishment."

The blast was so powerful that it rattled windows on the Mediterranean island of Cyprus, about 100 miles (160 km) away, reports said. 

How to measure an explosion's yield

The yield of an explosion is usually measured in kiloton. One kiloton yield is equal to the energy released in an explosion of 1000 tons of TNT (Trinitrotoluene).

One tonne TNT approximately releases 4.184×10^9 joules energy. Thus, one kiloton yield equals 4.184×10^12 joules or 4.184 tetrajoules or TJ. 

Biggest non-nuclear tragedy recorded in human history

The title of the biggest artificial explosion before the advent of the atomic bomb is held by Halifax city in the Canadian province of Nova Scotia. On December 6, 1917, a ship carrying tonnes of explosives -- SS Mont-Blanc -- collided with a relief vessel in the harbour of Halifax. Mont-Blanc was carrying 2,653 tonnes of various explosives, mostly picric acid, and the collision set off a series of explosions. The ship drifted into town and levelled buildings in a radius of over 1,600 feet while other structures in the city beyond this circumference were also destroyed. 

As per official records, 1,963 were killed, 9,000 were injured and another 6,000 were left homeless. 

Later, an evaluation of the explosion's force put the yield it at 2.9 kilotons of TNT (12 TJ). Halifax Explosion remained the biggest largest human-caused blast until second world war where the largest conventional bomb used was 10 tons of TNT. At the fag end of the World War II, the distinction for the largest bomb went to a nuclear bomb code-named "Little Boy" which was dropped on the Japanese city of Hiroshima on August 6. 

Hiroshima bombing 

The first atomic weapon which was dropped on Hiroshima on August 6, 1945 had a yield of approximately 13 kilotons. Estimates for the "Little Boy" have ranged from 6-23 kt but the current official yield is 13 kt. 

Another atomic bomb - Fat Man- was dropped on Nagasaki on August 9. The yield of the "Fat Man"  is said to be 23 kt.

Comparing Beirut explosion with Halifax, Hiroshima blasts

While experts are yet to determine the official yield of the explosion, 2,750 tonnes of explosives (ammonium nitrate) definitely have a large impact. The mushroom cloud, levelling of a large part of the city and rising death toll point towards a major disaster. 

According to a statement issued by the Lebanese authorities following a meeting of Supreme Defence Council, 2,750 tonnes of ammonium nitrate is equivalent to 1,800 tons of TNT.

If one had to estimate the yield of this blast, it would be around 1.8 kt or higher, two-third of the Halifax blast and nearly 15% of the yield of the Hiroshima bomb. Although it is unfair to compare a conventional bomb with a nuclear bomb, the energy yield can give you an idea about the impact of the Beirut blast. 

While the death toll is likely to rise, Beirut Governor Marwan Abboud said about 300,000 people have been displaced in the Lebanese capital and the cost of the destruction exceeds $3 billion. 

The official estimated the amount of damage from the explosion at around $3-5 billion while much of grain storage for the city has been destroyed.