In 10 days' time, Kenneth Feinberg will enter a room in Boston packed with victims of the marathon bombing and their families, for the first of two town hall meetings to discuss how to distribute compensation funds raised in the wake of the tragedy. He has been in many such encounters before, and knows all too well what to expect.

"It's harrowing. It's very emotional and very traumatic. It has to be done, I want to hear what people have to say, but you have to brace yourself for a very difficult couple of hours," he says. "Unless you have a heart of stone, you can't help being adversely impacted by hearing people express their anger, frustration, disappointment, concern about the uncertainty of life."

Feinberg is something of an expert on the uncertainties of life. Over the past two decades he has become the go-to guy for the administration of funds to disaster victims. It began in the 1980s, when the Washington-based lawyer helped settle a $180m class-action suit brought by Vietnam veterans impaired by Agent Orange, and it snowballed from there. He was at the helm of the massive effort to compensate victims of 9/11; he stepped into the hornets' nest of the BP oil spill in the Gulf of Mexico; and he distributed funds for those caught up in the mass shootings at Virginia Tech and Aurora, Colorado.

This highly rarified specialism has earned him the nickname "settlement czar" or, more snappily, the "master of disaster". So it surprised no-one that he was appointed days after the Boston marathon bombing to administer the One Fund, a charitable resource set up to help families of the four people who died and the more than 180 who were wounded.

Despite his lengthening experience in the grim world of man-made tragedies, Feinberg says the horror "doesn't get any easier. It's unimaginable what people can do to one another." But he has also been repeatedly amazed by the flip-side of disaster: the desire to help.

It is an amazing thing, the charitable impulse of the American people. The nation rallies around people in times of horror and tragedy and comes to the rescue – it's astounding to me.

This time it's personal. Feinberg, 64, was brought up just south of Boston in Brockton, Massachusetts. The fact that he is returning as a local boy will certainly make the task even more sensitive, but he doesn't think it will impinge upon his objectivity or professional determination to "do this right".

The core challenge facing him in Boston, as with previous missions, is to find the formula, or what he calls the "compensation protocol", that will allow money to go out the door as fast as possible. That involves defining who is eligible and how to calculate their entitlement.

In the case of 9/11, Feinberg's team calculated economic loss plus pain and suffering and put a figure on it, ranging from $10,000 to $1.5m. After last year's Aurora cinema shooting, families of the 12 who were killed were awarded $220,000 each, but Feinberg decided that the same amount should be given to several people who suffered horrific injuries, including those who suffered brain damage and one who became a quadriplegic.

That will be one of the early decisions to be taken in Boston, once people have expressed their opinions at the town hall meetings on 6 and 7 May – how much to award the families of the four dead (three at the marathon itself and the MIT police officer Sean Collier, who was killed during the suspected bombers' getaway); and how much to award the injured.

An emergency responder and volunteers push Jeff Bauman in a wheelchair after he was injured in the Boston Marathon bombings. Photograph: Charles Krupa/AP

The unique quality of Boston, Feinberg says, is the maiming caused by the cruel pressure cooker bombs placed on the street, where they wrought havoc with spectators' lower limbs. "The physical injuries were horrific – double amputees, single limbs removed, hospitalization for weeks and weeks."

How do you begin to put a monetary value on any of that?

"How long the person spent in hospital, that's a pretty good indicator," Feinberg says. "Someone in hospital for a month is considered more seriously injured than someone in overnight. You try and come up with a formula that ties compensation to hospitalization, say, and that will go a long way to solving the problem."

The latitude with which injuries can be compensated depends on the funds available. In Aurora, the $5.4m fund was just too small to do anything other than help the families of the dead and the physically injured – there was nothing left for emotional or psychological trauma. In the case of Virginia Tech, he was able to go one step further with the $8m at his disposal, though he drew a firm line. He did compensate for mental trauma, but only for those students who actually witnessed Seung-Hui Cho murder 32 people.

The Boston One Fund has already raised more than $25m, from a combination of individual and corporate donors. But given the scale of the tragedy, that is relatively tiny: "Considering the seriousness of the physical injuries, I'm not sure there'll be anything near enough for emotional trauma in Boston," Feinberg says.

The discrepancies are vast in terms of the financial muscle available to him. After 9/11 there was $7bn of government money to play with, and in the Gulf of Mexico disaster BP provided $20bn, making the One Fund look like a grain of sand. Besides, Feinberg is deeply aware that there never will be enough money, not even if you offer the Earth.

It's very difficult to me. You are never going to satisfy anybody in these programs, nor should you expect to. These are people who have suffered grievous, horrible loss, traumatic, unexpected, the idea that any amount of money is going to compensate them for their loss… forget about it.

At times, he has had bereaved individuals say to him: "I don't want your money. I want my dead daughter back, why don't you give me that." He has been forced to reply: "I haven't got the power to do that, I'm sorry, all I can do is very small, to give you some financial stability."

After all these years, Feinberg has come to realize the extreme limitation of what compensation can achieve. "All it does is provide victims with one less thing to worry about, I suppose. Apart from that, it's very hollow, it doesn't ring. It cannot make families whole, it will not replace a loved one, it will not assuage in any way their anger or frustration."

Feinberg has regularly found himself in the middle of bitter disputes, of the kind that erupt when people have been pushed to the limits of human endurance. Isn't that a burden for him at times?

"A burden at times?" he scoffs. "It is a burden at all times. At all times it's stressful, at all times you are in the middle of an emotional battle between families, and friends. It goes with the territory."

When they asked Feinberg to administer the One Fund, the governor of Massachusetts, Deval Patrick, and the mayor of Boston, Thomas Menino, set him a clear mission: to distribute the funds fairly, reasonably and as quickly as possible. He wants claimants to file in May, checks to start going out in June and most of the money to be distributed by July. Feinberg will be holding tight to that mission as he walks through the door on 6 May.

"You go in bracing yourself," he says, "not expecting thank yous and gratitude. Because you're not going to get it."