Charlton Heston starred in a number of science fiction movies in the 1970s, including Planet of the Apes, The Omega Man, and Soylent Green - all of them based on successful novels: Monkey Planet by Pierre Boulle; I Am Legend by Richard Matheson; and Make Room! Make Room! by Harry Harrison respectively.
In 1978, an edited selection of Heston's personal journals were published as The Actor's Life: Journals 1956 - 1976. There are only very brief mentions of the film in its pages, but this snapshots give some insight into the making of the movie.
The first mention of Harry Harrison's book is in an entry for 6th April 1968: "Read a book on the population explosion ... Let's see if anyone likes it but me." Heston's initial attempts to get the studios interested in the books as a movie project seem to fail, as the next reference is 6th February 1970, when he refers to an 'abortive move' to reactivate it as a project, while on 13th April 1970 he wrote "We've struck out with Make Room! Make Room!"
26th August 1971 saw a possible rekindling of the project after Heston entered discussions with Walter Mirisch at MGM for several possible movies, including Make Room! Make Room! Discussions continued through to 20th May 1972, with Walter Seltzer - with whom Heston had worked on several films before - now involved: one of the biggest problems to be overcome if the film was to be made was "how to suggest a city of eight million people without huge numbers of extras" - if a way could not be found of tackling these crowd scenes without huge numbers of (expensive) extras, then the film stood little chance of getting made.
By this point a script had been written: Heston reports that he had 'a long discussion' with the people at MGM about the script, which he felt had a weak final scene - "The whole payoff on the cannibalism element lacks impact ... Nevertheless, the script is better than it was. I'm beginning to have a very good feel for this one."
30th May Heston reports that MGM propose to change the title from Make Room! Make Room! to Soylent Green, of which he says "I like it."
7th June 1972 Richard Fleischer is first mentioned as a possible director. On 22nd June Heston had his first working meeting with Fleischer after he'd agreed to direct.
24th July Heston reports that MGM are keen to have Soylent Green in time for Christmas, this eagerness prompted by the success of Heston's previous films Skyjacked and The Omega Man. Delivery of the completed movie in such a short time was "simply not possible."
Casting the film began slowly, with Heston complaining on 4th August of little progress being made: "No girl has impressed me very much." MGM had made an offer to Edward G. Robinson to do the movie: they had offered him $25,000 up front, plus $25,000 deferred. Robinson's reply: "At seventy-nine, I'm not much interested in deferrals." Heston expressed the hope that they'd pay whatever it took to get him.
By 14th August, the major casting decisions had been made: Edward G. Robinson, Joseph Cotton, Leigh Taylor Young, and Chuck Connors had all signed, and Brock Peters was a probable. "This is a pretty formidable group ... I'm impressed."
Soylent Green began shooting on 5th September 1972. There was a brief break in shooting between 11th and 17th September due to the death of Richard Fleischer's father: Max Fleischer was a pioneer in the field of animated cartoons - his studio created Betty Boop among others.
Shooting resumed on 18th September with the 'love scene' between Heston and Leigh Taylor Young: "As written, it was slightly more explicit than we shot it; we're determined on a PG rating. Besides, I'm convinced there's no creative gain in playing these scenes nude. I've yet to see a film love scene that gained in erotic content by stripping the actors." Heston's only other comment on the filming of movie love scenes: "At least bed scenes are usually comfortable."!
Shooting of the apartment scenes between Heston and Edward G. Robinson were completed on 7th October: "Eddie Robinson's a lovely actor to work with. The chemistry between us is good."
16th October brought the shooting of the crowd scenes. The expense had been reduced by hiring a few hundred union extras at Extras Guild Rates, and the rest from outside the union, around 500 people in total, but still fewer than were really needed. Matte shots would be used to make it appear that there were in fact 40 million people in New York City in 2022.
Shooting of Soylent Green wrapped on schedule on 3rd November. Heston's verdict at the time: "The film is good."
Post-production work on the film continued into January 1973, with Heston going in to 'loop' dialogue.
The next mention that the film gets in Heston's journals is for 5th April 1973, in relation to a series of press events to promote the film in Philadelphia.
25th June 1973: Heston wrote: "I found that Soylent Green has opened to 'smash business in London and Tokyo.' This is a common sort of public relations quote, but it certainly means we aren't a flop."
18th March 1974: Heston reports that Soylent Green is doing well in 'foreign venues.'
Although Planet of the Apes is probably the best known of Heston's science fiction movies, Soylent Green is the one he has been most ready to talk about in the year's since its release. In a 1985 interview on British television he dismissed Planet of the Apes as "just a fantasy," but said of Soylent Green: "I think the population problem is the greatest problem the world faces. If we do not solve population, never mind any of the rest - never mind civil rights; never mind nuclear power; never mind the environment - it's all finished. And, of course, that's what Soylent Green was about. I'm very glad we made that, and very glad it was a success."